The William KROLL family in Luxembourg
My interest in the Kroll family was prompted by my friend R.M. who, as a child, had met William (Wilhelm, Guillaume) Kroll in the 1950s. William Kroll used to visit his 2 brothers living in the rue des Fleurs in Grevenmacher, a few houses down from where R.M. used to live. When William came to Grevenmacher (in his silver Mercedes car with a “red” Belgian number plate) to visit his 2 brothers Adolphe and Paul, he brought chocolate for the children in the neighbourhood … Adolphe and Paul had been living in Grevenmacher since the 1930s and were well known and respected.
In the course of my initial investigation I found out that I grew up close to William Kroll’s laboratory in avenue Gaston Diderich in the Belair suburb of Luxembourg City. William Kroll lived in number 44 (which later became number 54) and I lived in number 132 of the avenue. My school was situated opposite his laboratory and I vividly remember collecting chestnuts from the huge tree in front of the villa William Kroll had lived in. This was after 1952, when William Kroll had already closed his laboratory, so I could not have come across him on my way to school.
Lastly, when I recently visited with R.M. the Kroll family grave in the Cimetière Notre-Dame in Luxembourg and when I found out that as recently as 2018 the Lycée technique of Esch-sur-Alzette had been renamed Lycée Guillaume Kroll, I decided to find out more about William Kroll and his family in Luxembourg.
I started my investigation of the Kroll family with Carl Friedrich August Kroll, William’s grand-father.
Carl Friedrich August KROLL
Carl was born in 1808. On 4 August 1835 he married in Münster Regina LAPORTE, born in 1811. The marriage Register in Münster gives a minimum of information on the couple (empty spaces in the Register form), as compared to other marriages celebrated at the time  .
The later events show that bride Regina was pregnant at the time of the wedding since her first child Joseph Carl is born only 3 months after the wedding, namely on 8 November 1835. Joseph Carl was declared as being the legitimate child of Carl and Regina  .
Judging from the birth records of the successive children, it can be deduced that the family moved around 1841 from Münster to Dorsten (about 60 km away) and around 1848 from Dorsten to Bocholt (about 60 km away) in a triangular region north of Duisburg. A list published on Wikipedia (Liste der Bürgermeister der Stadt Dorsten) confirms that Carl was mayor of Dorsten from 1842 to 1848. He was thus a professional full-time mayor as shown in the 1849 Census report of Bocholt. The composition of the Kroll-Laporte family at the time was the following :
Mayor Carl (Friedrich August) KROLL’s family is composed of the parents and of 7 children. The family employed 2 servants.
The KROLL-LAPORTE couple had an eighth child in 1839 (Ferdinand) who only reached the age of 3.
The last-born of the family, Hermann, was born in 1852 as can be seen in the Bocholt Census of 1855. This Census also reveals that the 2 oldest children Joseph Carl (aged 20) and Paul (aged 18) had left home, Bertha now being the oldest child in the household .
The genealogical records of the UK show that the oldest son Joseph Carl moved to the United Kingdom where he married Agnes TOOTELL in Manchester on 13 December 1860. In the wedding records Joseph Carl is now referred to as Charles KROLL LAPORTE as he took on the name of his mother to create a double family name. In 1861 the first child born to the couple took on the family name LAPORTE (dropping the name KROLL) and all the children born later took on the name of LAPORTE. Charles himself became Charles LAPORTE in the census of 1881. He was a language teacher.
Among all the children of Carl and Regina, only Adolph Maria Gustav is to be found in the genealogy databases. The descendants of the other 6 children of Carl and Regina seem to have had little interest in their family tree.
Adolph Maria Gustav KROLL
Adolph (Maria Gustav) KROLL was born on 7 September 1849 in Bocholt .
Bocholt is a small town in Nord Rhein Westfalen (Germany) about 40 km north of Essen, close to the Dutch border.
Adolph was the second-but-last of the 9 children of the couple Carl Friedrich August KROLL & Regina Josephine LAPORTE. The LAPORTE family is of French origin and emigrated to Germany under LOUIS XIV. 
Nothing more is known about Adolph before the year 1875, other than that
• he studied in Berlin and Clausthal :
Après avoir suivi les cours du Professeur Wedding à Berlin il vint finir ses études à l’Ecole des Mines très renommée de Clausthal.
• he was drafted to serve in the 1870 Franco-Prussian war, as mentioned in the announcement of his death in 1930:
“Vétéran de la guerre de 1870” (veteran of the 1870 war). 
In 1875 Adolph moved to Belgium where he took on a job in the steel industry. He lived in Tilleur (close to Liège) and was an engineer at the local steel plant. He met Laure Joseph GRAFTIAU, the daughter of Jean François GRAFTIAU who was the director of the local mine. Laure was born on 3 March 1849 in Couthuin (Huy).
On 14 December 1880 Adolphe and Laure married in Couthuin.
Soon after, their two oldest sons were born in Couthuin, François (1881) and Adolphe (1882).
In 1882 Adolph was Director of the Société métallurgique de Sclessin-Angleur and in 1884 he moved with his family to Halanzy where he took on the job of Director of the Société métallurgique de Halanzy. Halanzy is situated in the extreme south-east of Belgium, close to France and Luxembourg.
Two more sons were born in Halanzy, Paul (1884) and Lucien (1886).
On 25 July 1887 Adolph, up to then a German citizen, took on Belgian nationality (and nearly lost it for failing to complete the required procedure). 
In 1888 the KROLL-GRAFTIAU family moved from Halanzy to nearby Esch-sur-Alzette in Luxembourg, where Adolph took on his next assignment as Fabrikationschef der Luxemburger Hochöfen-Gesellschaft, locally known as “Brasseurs Schmelz”.
The Obermosel-Zeitung in its edition of 28 February 1888 reported on a celebration for honouring local alderman and member of Parliament Léo METZ and mentions in passing: 
Es gratulierten noch mit je einem Bouquet in der Hand die HH. Kroll, Fabrikationschef der Luxemburger Hochöfen-Aktiengesellschaft …
On 10 August 1889, William Justine Adolphe KROLL was born in Esch-sur-Alzette. 
William was baptised on 1 December 1889 in the Saint Joseph Church in Esch-sur-Alzette. His godfather was uncle Wilhelm KROLL (*1848) from Krefeld, and his godmother was Justine MACKEL from Esch-sur-Alzette, whose husband substituted for Wilhelm (absent). Godfather “Wilhelm” and godmother “Justine” gave the first two names to the newly-born. 
The use of a female first name like “Justine”, as recorded in the civil register, was unusual in Luxembourg but commonly used in Belgium where William’s mother came from. The officiating priest at the baptism, however, chose the male Latin equivalent “Justinus”. The third Christian name appearing in the Civil Register, Adolph, was not recorded in the Church Register and was never later associated withWilliam.
The first Census sheet in Luxembourg in which the KROLL-GRAFTIAU family appears is dated 1 December 1890 and gives the address of the family as 8 rue d’Audun (Otherstrasse) in Esch-sur-Alzette. It shows the following family composition (all members of the family are citizens of Belgium) :
It is interesting to point out at this stage that the Kroll son born in 1886 as Lucien Adolphe Félicien is referred to as Léon. All later published references mentioning him use the first name Léon.
The Esch-sur-Alzette 1 December 1895 Census adds the last son Théodore born in 1894 to the long family list .
The Census also points out that François (aged 14) and Adolphe (aged 13) were absent from home because they were studying in Luxembourg City, giving evidence that they were living at the time in a “boarding” house in Luxembourg City, probably the so-called “Convict”, temporary home at the time for many Athénée students living outside the city of Luxembourg .
The following table illustrates William KROLL’s family tree, including the Luxembourg-born partners of his brother François and his sister Elvire.
The “presence” of the KROLL-GRAFTIAU family in Luxembourg generated the following “news” as reported in the local press after their arrival in Luxembourg in 1888:
In 1890 Adolph was promoted from Fabrikationschef to Directeur-gérant of the Luxemburger Hüttenwerke  and in 1892, when the company merged with the Aachener Eisenhüttenverein “Rothe Erde”, he was appointed liquidateur of his former company and became Generaldirektor der Aachener-Hütten-Aktien-Gesellschaft, Abteilung Esch, Hochöfen und Grubenbetrieb in the new company .
In later years Adolph Kroll was regularly mentioned in the local press as he had to deal with issues affecting the local community such as:
- a gas explosion in 1895 in one of his factories 
- in 1896, Adolph was taken to court by a local publican who sued him for damages, claiming that Adolph had forbidden the workers of Aachener-Hütten-Aktien-Gesellschaft to visit his establishment. Adolph won the case …. 
In 1896 Adolphe was obviously not happy with the taxes imposed to him personally by the Administration des Contributions and he filed an appeal against its decision before the Conseil d’Etat (Comité du contentieux). However, the case was taken off the role in 1897, upon demand of both parties , presumably having reached agreement in the mean time.
The local steel industry went through more mergers …
In the year 1899 Adolph Kroll was founding member of the Société métallurgique de Sambre et Moselle à Charleroi et Maizières and became its administrateur-délégué.  This is the moment when Adolph, aged 50, is no longer involved in the day-to-day management of the local Luxembourg steel works. His name thus no longer appears in the local press.
The Revue Technique Luxembourgeoise of 1973  gives further details about Adolph’s history:
En 1890, il passa à Esch-sur-Alzette pour diriger l’usine actuelle de Terre Rouge. C’est grâce à son rapport sur le domaine minier de la frontière luxembourgeoise que l’Aachener-Hütten-Aktien-Verein l’a acquis vers 1900. Adolphe KROLL fut le premier à remarquer l’utilité d’augmenter la teneur en phosphore des fontes Thomas en y ajoutant des craies phosphatées naturelles au haut fourneau. Il fonda la « Phospho-Métallurgique »  qui lui assura une situation matérielle enviable … Renversé par une automobile il subit une fracture du crâne dont il ne devait se remettre que pour diriger ses six fils vers la carrière de l’ingénieur qu’il avait tant aimée.
At the beginning of 1900 Adolph bought a villa in Luxembourg City situated on the outskirts of the city park on 12 rue Joseph II.  
The Census of 1 December 1900 shows the composition of the family at the time as follows :
Although the Kroll villa was in fact situated on 12 rue Joseph II, it was also referred to as 12 place Joseph II . It was indeed situated on the edge of the parc looking onto the place Joseph II. The Kroll villa was demolished in the 1960s (?) to make place for a large apartment building.
After the year 1900, the local Luxembourg records provide only sporadic news about the Kroll family members (see later).
However the school results of the sons published at yearly intervals give a further insight into their academic development. (In the early 1900s school results of girls are not considered worth mentioning in the press!)
Academic record of the KROLL sons
On 12 August 1895, the Luxemburger Wort reported that the eldest son Adolphe was studying at the Athénée in Luxembourg and that he had been awarded “Accessite” honours in Zeichnen (drawing) and in Turnen (gymnastics) . He was in the Vorbereitungsklasse (first year, Septima). This is the first mention in the local press of the school results of the Kroll sons but not the last one. Their achievements can be summarised as follows:
• 1896: Accessite award in Zeichnen (drawing)
• 1898: Ubergangsprüfung nach Quarta
• 1902: Reifeprüfung am Gymnasium
• 1906: Diplomingenieur Berlin Charlottenburg
• 1895: Accessite award in Turnen (gymnastics)
• 1896: Accessite award in Turnen (gymnastics)
• 1897: Quinta, 9. Preis
• 1898: IV class (global), second Accessite award
• 1901: cours de dessin (drawing), Accesite award
• 1905: diplôme d’ingénieur des mines Berlin Charlottenburg
• 1898: Vorbereitungsklasse, Accessite award in Zeichnen (drawing)
• 1899: third price in Turnen (gymnastics)
• 1901: Reifeprüfung
• 1907: Industrie- und Handelsschule, Fähigkeitsexamen
• 1909: examen préparatoire pour le grade d’ingénieur des mines, Ecole polytechnique d’Aix-la-Chapelle
• 1911: examen d’Ingénieur, Breslau
• 1902: award in gymnastique
• 1908: Industrie- und Handelsschule, Fähigkeitsexamen
• 1910: école polytechnique de Berlin, examen de seconde année
• 1913: Königliche Technische Hochschule zu Charlottenburg , Diplom (Eisenhüttenkunde)
• 1905: 5. Klasse, award in Freihandzeichnen (drawing)
• 1906: Übergangsexamen
• 1911: examen comme candidat-ingénieur à Charlottenburg
• 1917: Doktor-Examen in Berlin mit Auszeichnung
• 1914: examen de maturité
• 1917: Technische Hochschule in Berlin-Charlottenburg , Vordiplomprüfung
• 1918: Technische Hochschule in Berlin-Charlottenburg, Diplom “Eisenhüttenkunde”
(It is interesting to note that some of the the Kroll brothers have a gift for “Zeichnen” (drawing) and are good sportsmen).
François KROLL (1881-)
Judging from the Luxembourg patents that François filed he worked as an engineer in the Belgian metallurgical industry:
N° 8.017 (8 July 1909), “Disque conique à vent chaud et anneaux-guides coniques”, Fr. Kroll à Régina-Huy.
N° 13.624 (20 August 1921), “Métal d’apport pour la soudure autogène du cuivre”, Fr. Kroll à Bruxelles.
On 23 April 1924, François KROLL and Mathilde HAMÉLIUS (born 16 February 1890 in Diekirch) married in Brussels. Mathilde was the daughter of Jean Ernest HAMÉLIUS, a lawyer who became Director of the Banque et Caisse d’Epargne de l’Etat and occupied such prestigious posts as Président du Conseil d’Etat, Président de l'Administration des Biens de la Couronne … 
Mathilde’s brother Jules HAMÉLIUS was a notary.
François and Mathilde, having married in Brussels, presumably settled there.
In 1939 Mathilde separated from François and returned to Luxembourg in the rue des Acacias; she applied for “la séparation des biens” (separation of goods) from her husband through a public writ (exploit d’huissier of 10 June 1939) … 
François and Mathilde had two sons, Raymond (1925) and Lucien (1927).
Raymond KROLL studied agronomy and moved to the Belgian Congo in 1948 where he worked as a planteur (planter) for the Huileries du Congo Belge. When the Congo became an independent state in 1960 he returned to Belgium. He is the author of several books on the culture of vegetables, fruit and flowers.
In 1997 he published his last book entitled “Un planteur belge au Congo” .
Raymond KROLL’s eldest child Pierre was born in 1958 in Congo. Pierre KROLL is currently (2020) one of Belgium’s best known cartoonists. Wikipedia gives an extensive account of Pierre Kroll’s work and achievements.
Lucien KROLL is an architect of international renown acclaimed for his ecological architecture.
Wikipedia writes the following:
Lucien Kroll (born Brussels, 13 March 1927) is a Belgian architect known for his projects involving participation by the future inhabitants of the buildings. His most famous work is the Medical Faculty Housing at the University of Leuven, Belgium, from 1970-76. These buildings aroused widespread controversy in the early 1970s, their fragmented and improvisational appearance - the result of a deliberate participatory design process - in stark contrast to the adjacent massive and repetitive hospital, the embodiment of a centralised bureaucracy.
Adolphe Maria Victor KROLL (1882-)
On 22 May 1911 Adolphe applied for his first patent in Belgium (“Processes for agglomerating finely-divided granular or friable materials”) and later, for the same invention, in France, the UK and in the US. He was 29 years of age and applied in his own name, as a private inventor. His address was given as 12, place Joseph II in Luxembourg (GB patent 27762/1912), i.e. the home of his parents.
In 1929 he obtained an additional patent in the US on an improvement of the process of the 1911 invention and on an apparatus for carrying out the process. Up to this date he was still registered as living in Luxembourg City, but when Adolphe applied for patents in 1932 and 1934 his residence was Grevenmacher.
When the family home in Luxembourg was sold in 1931, Adolphe moved to Grevenmacher (rue de l’Ecole). His brother Paul, who was also a bachelor and was still living in the family home in 1930, moved with Adolphe to Grevenmacher. Katharina RONCK, housekeeper of the Kroll family in boulevard Joseph II since 1921, also followed the Kroll brothers in their move.  .
The fact that Adolphe assigned his later “lithium-related” patent rights to the Congolese company Geomines suggests that he worked in the Belgian Congo in the 1920s before settling in the family home and later in Grevenmacher. 
He was still living in Grevenmacher in 1938 when housekeeper Katharina RONCK died. Later in the year, however, Adolphe and Paul wished to move house.  It is possible that this change of residence took place only in 1941 when the brothers moved to 4 rue des Fleurs in Grevenmacher. 
When Adolphe moved to Grevenmacher around 1931, at the age of 49, he engaged in the culture of grapes and wine-making. This is reflected not only through his patent application of 1934 (Stützvorrichtung im Boden für dünne Stäbe, namentlich Weinbergpfähle, see above) but also from a newspaper report of 1935 which mentions that Adolphe provided Muscat grapes to the Neudorf Traubenkurstation .
As of 1936 Adolphe presented samples of his wine production to the Committee awarding the Marque Nationale label and earned credit for his Traminer-Riesling, Muscat-Traminer and Riesling-Sylvaner wine production.
In 1938 he was chosen to supervise the EXID experiment in his vineyard “Wenigfels”. 
The local vineyards in Grevenmacher, situated close to woodland, were plagued by birds which fed on the grapes. An apparatus by the name of EXID was installed in the “Wenigfels” vineyard. It was a “Schreckschuss-Kanone” which is meant to scare away the birds. The canon emitted an explosive noise at regular intervals thus producing the desired effect. The experiment, under the supervision of Ing. Adolphe Kroll was reported to be successful.
In 1939 Adolphe created a company by the name of Société Commerciale et industrielle d'engrais et produits chimiques “le Volcan” in Grevenmacher . The object of the company was: “Erzeugung und Vertrieb aller chemischer und mineralischer Produkte unter besonderer Berücksichtigung von Düngern, Insektenvertilgungsmitteln und Farbstoffen” and in 1945 Adolphe published a scientific article under the title: “Die wissenschaftlichen Grundlagen der Atombombe”.  The article is purely of a didactic nature aiming to explain in a simple manner the mechanism of an atomic bomb.
Paul KROLL (1884-)
In 1921 (at the age of 37) Paul obtains a patent in Luxembourg in his own name. The Mémorial of 1922 gives the following information:
N° 12261 - 4 mai 1921 - Procédé nouveau de coulée à lingotières, servant à réduire a) le volume, b) la section, c’est-à-dire la hauteur, de la retassure des métaux et produits coulés, de sorte à obtenir une perte par déchets minimum. - Paul Kroll, ing. dipl. à Luxembourg.
A corresponding patent was filed in Germany where it issued under No 357,966.
Paul Kroll filed two additional patent applications in Luxembourg on non-scientific matters. They are described in the Mémorial in the following terms:
N° 14246 - 25 novembre 1925. - Cerceau protecteur pour cabinets à sièges. - Paul Kroll à Luxembourg.
N° 16949. — 30 août 1929 - Dés-transposeurs interchangeables pour claviers de machines à écrire. - Paul Kroll à Luxembourg.
In 1932, Paul lived in Grevenmacher. This can be seen from an article that he wrote in the Revue Technique Luxembourgeoise (Bulletin de l’Association Luxembourgeoise des Ingénieurs et Industriels) in the January/February issue of 1932 under the title “Berechnung und Messung des Lunkervolumens”, a terminology used in the diecast industry .
Paul bought a vineyard in 1933 in Grevenmacher, in the part known as “in der Loch” for setting up an experimental fruit tree garden. This transaction, including the declared intention of the buyer, was reported in the Luxemburger Wort as well as in the Obermosel-Zeitung . Paul’s objective was to test the growth of new types of fruit in the Moselle valley. The interest in this project among the locals was such that the local press reported the successful growth of melons (1935)  and (ripe!) almonds (1936) , the latter fruits in the “Schiffmühlenweg”. The local reporter stated:
Da der Mandelbaum ziemlich reichlich trägt und sozusagen keine Pflege erfordert, ist es nicht ausgeschlossen, daß diese Kultur eine neue Einnahmequelle für unsere Moselgegend erschließen wird.
The Obermosel-Zeitung reported in 1935  that burglars stole grapes in Paul’s fenced-in vineyard “auf Wengels”and on two occasions, in 1938 , and in 1946 , the local paper reports that Paul’s weekend home in the vineyards was vandalised. The 1946 publication concluded with the following sentence:
Im Laufe von fünfzehn Jahren wurde mindestens zehnmal eingebrochen und man vermutet, daß es sich stets um denselben Täter handelt.
Lucien (Léon) KROLL (1886-)
Théodore KROLL (1894-)
On 24 May 1892 the Obermosel-Zeitung writes :
Vor einigen Tagen wurde auf den Lux. Hochöfen der neuerbaute dritte Ofen, welcher zur allgemeinen Zufriedenheit ausgefallen ist und seinen Erbauern, Hrn. Direktor KROLL, sowie auch Hrn. Fabrikationschef Gredt, alle Ehre gemacht, in Betrieb gesetzt; vorher hatte Hr. Peiffer den Ofen eingesegnet; das 5 jährige Söhnchen des Hrn. Kroll zündete den Koloss an …
The Kroll son mentioned here must be Lucien Kroll although Guillaume Kroll, in his extensive article entitled “How commercial titanium and zirconium were born” published in the Journal of the Franklin Institute  reports a similar experience in the following words:
A far away picture still remains in my mind, when, as a child, in the darkness of a cold morning I was taken out of bed to light a new blast furnace with a - bunch of cotton, impregnated with burning kerosene and fastened to the tip of a long pole.
Guillaume Kroll probably reflects on a later event, similar to the one reported in the press in 1892.
Once Lucien and Théodore had obtained their University degree their names were no longer mentioned in the local press. It is to be noted though that Théodore applied for and received the Luxembourg nationality in 1914 before going off to Germany for his studies. He thereby gave up his Belgian nationality . However, later in life he must have settled in Rhode St Genèse (Brussels) as he was joined there by his brother William in 1961 leaving the US to settle in Europe.
Both Lucien and Théodore, either lead a low-key life in Luxembourg or made their living elsewhere …
Elvire KROLL (1891 - 1967)
Daughter Elvire Kroll was mentioned only once in the local press in 1913 as a tennis player in the newly created local club “Sporting” .
In 1918, at the age of 27 Elvire Kroll married Paul CRAVAT, a judge at the Luxembourg Tribunal d’arrondissement (District Court) . Paul was aged 36. The couple had two daughters, Milly and Simone. Paul Cravat later left the magistrature to become a notary. He died in 1947 and did not live to witness the engagement of his daughter Milly to Henri EDINGER in 1948  .
Elvire Kroll died in 1967 and is buried in Luxembourg-city in the grave of the Cravat family.
Daughter Simone did not marry and lived in Luxembourg where she died in 1994, aged 70. She is buried next to her mother Elvire.
Milly CRAVAT and Henri EDINGER had two daughters by the name of Christiane and Claudine.
Guillaume (William) Justine KROLL (1889-1973) 
As seen above, William was born in Esch-sur-Alzette in 1889, but in 1900, at the age of 11, he moved to the centre of Luxembourg City in the family villa situated 12 place Joseph II (renamed place Winston Churchill in 1973). He followed his secondary studies in the Athénée Grand-Ducal where he passed his Übergangsexamen in 1906  and obtained his baccalauréat in 1909.
In 1910 William Kroll acquired the Luxembourg nationality (thereby resigning his Belgian nationality)  and in 1912 he was a founding member of the student association ASOSS (Association générale des étudiants luxembourgeois). 
The local press reported his successful examination as candidate-engineer in 1911. 
At the end of 1916/beginning of 1917 William filed his first patent applications leading to the so-called “Lurgi-Metall”, even before he obtained his doctorate . (“Lurgi” is the name of the research department of the Metallbank und Metallurgische Gesellschaft A.G., William’s first employer to whom he assigned his patent rights.)
The Luxemburger Wort reported in February 1917 that William had obtained the title of Dr.-Ing . His doctoral thesis was entitled “Über die Darstellung des amorphen Bors” .
In 1917 William filed additional patent applications in his own name relating to alloys of the alkali-earth metals.
William’s mother died in 1919. 
In the years 1920 to 1923 William gave the following addresses as his place of residence:
1920 Frankfurt, 27 Humboldtstrasse
1920 Luxembourg, 12 place (boulevard) Joseph II (his parents’ home)
1922 Luxembourg, 52 rue Schmitz (Hollerich), renamed rue Albert 1er (Luxembourg) in 1925.
1924 Luxembourg, 54 Bel’air Strasse
William Kroll’s professional career has been extensively described by himself and by others. His research years in Luxembourg from 1922 to 1939 are described in this article:
The following dates summarise the major steps in his professional life in relation to Luxembourg:
- 1918 Leaves the Technische Hochschule Charlottenburg-Berlin 
- 1918 Association with “Metallbank und Metallurgische Gesellschaft A.G., Frankfurt am Main” and assignment to Bleihütte Kall GmbH, Eifel
- 1919 Contract inVienna
- 1920 Contract from the Hungarian State to work in Kombinat des Manfred Weiss Werkes, Csepel, Budapest  
- 1922 Contract for setting up a foundry in Baden-Baden, development of Alusil, Alsia
- 1923 Return to Luxembourg
- 1924 Purchase of Villa Leclerc (Madeleine) in Belair 
- 1931 Consultancy with Heraeus Vakuumschmelze, taken over later by Siemens und Halske 
- 1931 (6 March) Trip from Bremen to New York on the ocean liner“Bremen”, US visa issued in Luxembourg on 19/02/1931 
- 1937 First work on titanium, basic patent application filed in Germany DE 674,625 (10 July 1937)
- 1938 (13 October) Trip from Cherbourg to New York on RMS “Queen Mary”, US visa issued in Luxembourg on 24/06/1938 
- 1938 Titanium is machined in the Cerametal factory in Bereldange
- 1940 (10 February) Emigration to the USA, leaving Rotterdam for New York on the ocean liner “Volendam”, US visa issued in Antwerp on 31/11/1939 
- 1942 (17 September) US patents are “vested” (seized) by the US Government
- 1947 Claim filed for the return of property of US patent 1,986,585 (Nickel alloy) and US patent 2,205,854 (Titanium)
- 1947 (July/August) visit to Luxembourg
- 1947 (6 September) Conference in Luxembourg under the title: “Titane et zirconium malléables, deux métaux nouveaux“, publication of the text of the conference 
- 1948 Offer for sale of laboratory equipment 
Sale of villa situated 54 avenue Gaston Diderich to the Luxembourg State ;
Membership of the Institut Grand-Ducal, section des sciences 
- 1948 (13 February) Return to Corvallis on ocean liner “Amsterdam” leaving Rotterdam for New York, US visa issued in Philadelphia on 02/07/1947 
- 1949 Publication in Chroniques des cahiers, Verdienste um das Zukunftsmetall Titan, G. Kroll 
- 1950 Resignation from U.S. Bureau of Mines, Oregon and becoming a private consultant in Corvallis
- 1950 US patent 1,986,585 (nickel alloys) court case, first decision 
- 1951 (3 April) US patent 2,205,854 (Titanium) court case, first decision
- 1951 (21 December) Return to Corvallis on RMS “Queen Mary” leaving Cherbourg for New York, Luxembourg passport
- 1952 (17 July) US patent 2,205,854 (Titanium) court case, second decision
- 1952 US citizenship 
- 1953 (22 October) Return to Corvallis on RMS “Queen Mary” leaving Cherbourg for New York, US passport
- 1953 (1 December) US patent 2,205,854 (Titanium) court case, third decision
- 1954 Publication in d’Lëtzebuerger Land of an extensive article under the title of: TITAN, das strategische Leichtmetall Nr. 1 und sein Pionier, der Luxemburger GIG KROLL, author unknown 
- 1954 (30 October) Return to Corvallis on ocean liner “New Amsterdam” leaving Le Havre for New York, US passport
- 1955 Election as honorary member of the Société des naturalistes luxembourgeois
“M. William J. KROLL, ingénieur-conseil à Corvallis (Oregon, U.S.A.), pour ses remarquables travaux concernant la préparation industrielle des métaux rares.” 
- 1955 Publication of an article by William Kroll in the Journal of the Franklin Institute entitled: "How commercial titanium and zirconium were born" 
- 1955 (8 September) Return to US on RMS “Queen Mary” leaving Cherbourg for New York 
- 1956 Publication in the d’Lëtzebuerger Land of an article for the attention of the local people entitled “Titan und Zirkonium, ein erlebtes Märchen”, signed J.W. Kroll 
- 1956 (26 October) Return to US on RMS “Queen Mary” leaving Cherbourg for New York 
- 1960 US patent 2,205,854 (Titanium) court case, fourth decision 
- 1961 Return to Europe and settling in Rhode St Genèse, Brussels, close to youngest brother Théodore 
- 1962 Publication in the d’Lëtzebuerger Land of an extensive article under the title: Luxemburger Wissenschaftler im Ausland, W.J. KROLL, signed S. 
- 1963 Publication of an article by William Kroll in d’Lëtzebuerger Land under the title: “Die Krise im Errziehungswesens” 
Conference before the Société luxembourgeoise des Naturalistes entitled: ”Le titane et ses applications” 
- 1964 US patent 2,205,854 (Titanium) court case, last decision 
- 1965 Publication of an article in d’Lëtzebuerger Land under the title: Die sozialen Folgen der Automation, signed William Kroll 
Publication of an article in d’Lëtzebuerger Land under the title: “Das Experiment und die Schriften”, signed William Kroll 
- 1969 Dr Honoris Causa des sciences appliquées of the Université libre de Bruxelles 
- 1973 Publication of obituary in d’Lëtzebuerger Land, signed Robert Stümper 
Guillaume Kroll died on 30 March 1973 in Rhode St Genèse, Brussels , and was buried on 4 April 1973 in Luxembourg-city in the grave of his parents .
Guillaume Kroll’s technical library
In 1970 Guillaume Kroll donated his library of about 500 books to the Association Luxembourgeoise des Ingénieurs . This collection was later transferred to the Archives Nationales where it is kept under the section of “Collections privées”. The collection includes a very valuable compendium entitled “The Collected Works of William Kroll” which contains complete photocopies of almost all of Kroll’s publications.
Guillaume Kroll’s bequest to science and industry
1965 Donation of titanium patent royalties (awarded in the final US court decision) to several US and European universities for research and scholarships .
1974 Bequest to the Colorado School of Mines for allowing this institution to establish KIEM (Kroll Institute of Extractive Metallurgy).
KIEM defines its mission in these terms:
Today, the mission of the Kroll Institute is to support the minerals, metals and materials industries through the following activities:
• Maintain expertise and research capabilities important to the minerals, metals and materials industries
• Perform cutting edge research
• Train process engineers for industry
• Develop short courses
• Develop specialty conferences
Medals and honours  
1954 Francis J. Clamer Medal of the Franklin Institute, Philadelphia
1954 James Douglas Gold Medal of the American Institute of Mines and Metallurgy
1955 Albert J. Sauveur Plaque of the American Society for Metals
1955 Heyn Denkmünze of the Gesellschaft für Metallkunde, Köln
1958 Perkin Gold Medal of the Society of Chemical Industry U.S.A.
1958 Edward Goodrich Acheson Gold Medal of the Electrochemical Society, U.S.A.
1960 Castner Gold Medal of the Society of Chemical Industry, London
1968 Platinum Medal of the Institute of Metals, London
Dr honoris causa
• Oregon State University (1953)
• Université de Grenoble (1955)
• University of Missouri, School of Mines and Metals (1958)
• Rheinisch-Westfälische Technische Hochschule, Aachen (1960)
• Dr honoris causa de l’Université libre de Bruxelles (1969)
1954 Ordre de la couronne de chêne, Luxembourg
1972 Creation of The W.J. Kroll Medal and Prize, Institute of Metals 
1975 (?) Creation of the William J. Kroll Zirconium Medal, ASTM International
1987 Creation of the Kroll Medal, The Institute of Materials, Minerals and Mining (IOM3) 
2000 Entry into the National Inventors Hall of Fame in the USA 
2018 Highschool in Esch-sur-Alzette named: “Lycée Guillaume Kroll” 
Creation of the Prix William-Kroll by the Association jeunes scientifiques Luxembourg
Road named rue Guillaume J. Kroll in Luxembourg City
Road named rue Guillaume J. Kroll in Esch-sur-Alzette
1 (The present note is in no way meant to be a historical or genealogical document as I have no qualifications in this respect.)
2 Matricula-online database
3 Matricula-online database
4 Census Bocholt 1849 5 Census Bocholt 1855
6 Matricula-online database
7 Revue Technique Luxembourgeoise, No 2, 1973, pages 67-68
8 Tageblatt, 09/12/1930, page 3
9 Sénat de Belgique, Séance du 27 juillet 1889, (S.109)
10 Obermosel-Zeitung, 28/02/1888, page 2
11 FamilySearch database
12 Matricula-online database
13 Census 1890 Esch-sur-Alzette
14 Census 1895 Esch-sur Alzette
15 Census 1895 Esch-sur-Alzette
16 Obermosel-Zeitung, 24/06/1890, page 2
17 Luxemburger Wort, 05/07/1892, page 3
18 Escher Courrier, 03/10/1895, page 3
19 L’Indépendance luxembourgeoise, 29/10/1896, page 2
20 Conseil d’Etat, Attributions en matière contentieuse, Feuilles d’audience, Numéro 961 du Rôle, (Archives nationales)
21 Luxemburger Wort, 11/02/1899, page 4
22 Revue Technique Luxembourgeoise, No 2, 1973, pages 67-68
23”La Phospho-Métallurgique”, company registered in Belgium
24 Luxemburger Wort, 05/02/1900, page 3
25 n° cadastral 713/1466
26 Census 1900 Luxembourg
27 renamed place Winston Churchill in 1973
28 Luxemburger Wort, 12/08/1895, page 3
29 Family tree Mouris-Bernard
30 Luxembourg, quotidien du matin, 14/06/1939, page 6
31 ISBN 2-7384-5225-6
32 Tageblatt 28/03/1931, page 3
33 Obermosel-Zeitung, 28/05/1931, page 4
34 Obermosel-Zeitung, 28/05/1931, page 4
35 Obermosel-Zeitung, 17/12/1938, page 15
36 Obermosel-Zeitung, 08/01/1941, page 6
37 Obermosel-Zeitung, 27/08/1935, page 2
38 Obermosel-Zeitung, 29/09/1938, page 7
39 Obermosel-Zeitung, 09/05/1939, page 4
40 Obermosel-Zeitung, 27/10/1945, page 2
41 Revue Technique Luxembourgeoise (Bulletin de l’Association Luxembourgeoise des Ingénieurs et Industriels) 1932, No 1
42 Luxemburger Wort, 08/03/1933, page 4; Obermosel-Zeitung, 08/03/1933, page 3
43 Obermosel-Zeitung, 17/09/1935, page 4
44 Obermosel-Zeitung, 15/09/1936, page 4
45 Luxemburger Wort, 21/09/1935, page 5
46 Obermosel-Zeitung, 14/11/1938, page 4
47 Tageblatt 18/10/1946, page 5
48 Obermosel-Zeitung, 24/05/1892, page 3
49 The Journal of the Franklin Institute, Vol 260, 1955, page 170
50 Obermosel-Zeitung, 12/05/1914, page 1
51 L’indépendance luxembourgeoise, 26/09/1913, page 3
52 FamilySearch database
53 Luxemburger Wort, 22/12/1948, page 5
54 Milly Cravat and Henri Edinger married in 1949 and lived in 42, avenue Guillaume, Luxembourg; Henri Edinger held a pharmacy in Luxembourg-city; it would appear that the two daughters of Edinger-Cravat are the last relatives of William Kroll in Luxembourg (in 2021).
55 FamilySearch database
56 Luxemburger Wort, 06/08/1906, page 2
57 L’Indépendance luxembourgeoise, 12/01/1910, page 3
58 Robert Stumper, In memoriam W.J. Kroll, d’Lëtzebuerger Land, 13/04/1973, page 3
59 L’Indépendance luxembourgeoise, 28/10/1911, page 3
60 DE 301380, DE 381577, DE 386602
61 Luxemburger Wort, 19/02/1917, page 2
62 William J. Kroll, “A Luxembourg Scientist”, Fondation Nicolas Lanners, 1998
63 Luxemburger Wort 18/08/1919, page 2
64 d’Lëtzebuerger Land, 09/03/1956, page 3
65 d’Lëtzebuerger Land, 09/03/1956, page 3
66 L’Echo des Naturalistes, No 3, 31 décembre 1962, pages 2-5, No 4, 21 mars 1963, pages 1-3, No 5, 5 décembre 1963, pages 2-4
67 L’indépendance luxembourgeoise, 28/08/1924, page 3
68 d’Lëtzebuerger Land, 10/12/1954, page 3
69 New York Passenger and Crew Lists, 1909, 1925-1957
70 New York Passenger and Crew Lists, 1909, 1925-1957
71 New York Passenger and Crew Lists, 1909, 1925-1957
72 Revue technique luxembourgeoise, octobre/décembre 1947
73 Luxemburger Wort, 05/01/1948, page 5
74 Tageblatt, 03/07/1948, page 6
75 Luxemburger Wort, 22/06/1948, page 2
76 New York Passenger and Crew Lists, 1909, 1925-1957
77 Luxemburger Wort, 08/01/1949, page 14
78 91 F.Supp. 173 (1950)
79 National Inventors Hall of Fame
80 d’Lëtzebuerger Land, Nr 50, pages 3/4 (author was probably Robert Stümper)
81 Bulletin de la Société des naturalistes luxembourgeois, 01/01/1955, page 133
82 Journal of the Franklin Institute,Volume 260, Issue 3, September 1955, Pages 169-192
83 New York Passenger and Crew Lists, 1909, 1925-1957
84 d’Lëtzebuerger Land, 09/03/1956, pages 3 & 6
85 New York Passenger and Crew Lists, 1909, 1925-1957
86 276 F.2d 385 (1960)
87 Article entitled W. J. KROLL: "A metallurgist of the unusual: the amphibious and recalcitrant lone wolf researcher”, signed John J. Moore
88 d’Lëtzebuerger Land, 08/06/1962, pages 3 & 6
89 d’Lëtzebuerger Land, 13/12/1963, page 7
90 Bulletin de la Société des naturalistes luxembourgeois, 01/01/1963, page 235
91 326 F.2d 975 (1964)
92 d’Lëtzebuerger Land, 23/07/1965, page 3
93 d’Lëtzebuerger Land, 08/10/1965, page 3
94 d’Lëtzebuerger Land, 13/10/1969, page 5
95 d’Lëtzebuerger Land, 13/04/1973, page 3
96 21 Drève des Chevreuils, Rhode St. Genèse, Belgique
97 Cimetière Notre-Dame, Grave VI 07 905
98 Luxemburger Wort, 19 mai 1973, page 10; no inventory of the collection has been made
99 Modern Metals, 1965, page 98
100 Luxemburger Wort, 05/01/1947, page 5
101 “William J. Kroll, A Luxembourg Scientist”, Fondation Nicolas Lanners, 1978, page 22
102 Metals and Materials, No 6, 1972, page65
103 The Institute of Materials, Minerals and Mining
104 National Inventors Hall of Fame
105 MÉMORIAL A N° 665 du 8 août 2018