2 Reminiscences of the Early Twenties RUDOLF BRILL
Downloaded by CORNELL UNIV on July 20, 2016 | http://pubs.acs.org Publication Date: December 10, 1981 | doi: 10.1021/bk-1981-0175.ch002
8172 Lenggries, Arzbacher Strase 6, West Germany
Shortly after the I. World War scientific life began to grow again in Germany. One of the famous scientific enterprises in this country, the Kaiser-Wilhelm-Gesellschaft, had several institutes in Berlin and a new one, the Kaiser-Wilhelm-Institut für Faserstoffchemie (Institute for Chemistry of Fibrous Material), was just founded. In this institute a very interesting discovery was made: the x-ray investigation of cellulose fibers showed that these fibers were crystalline, i . e . , x-rays were diffracted by them and the evaluation of the x-ray diagram resulted in a small elementary cell containing only four units of glucose. Since, by definition, the elementary cell must contain at least one molecule, the conclusion was drawn that cellulose has a low molecular weight of not more than four units of glucose. Consequently, an interscientific fight began and it might be that this interesting situation motivated Herman Mark to go from Vienna, where he had studied, to Berlin to join just that institute where the x-ray investigation of cellulose had been performed even though the situation there did not look too favorable: The j u s t founded i n s t i t u t e had no own b u i l d i n g yet and was l o c a t e d as guest i n the i n s t i t u t e of P h y s i c a l and E l e c t r o c h e m i s t r y of the Kaiser-WilhelmG e s e l l s c h a f t , headed by F r i t z Haber the famous inventor o f the t e c h n i c a l s y n t h e s i s of ammonia. However, there was not much space i n Haber s i n s t i t u t e and, t h e r e f o r e , the x-ray l a b o r a t o r y of the g u e s t - i n s t i t u t e was r a t h e r p r i m i t i v e l y l o c a t e d i n the basement of Haber s r e s i d e n c e . But t h i s i n no way impressed Mark. Obv i o u s l y he was very much i n t e r e s t e d i n the a p p l i c a t i o n of the new method of x-ray d i f f r a c t i o n . Consequently, he j o i n e d the group of P o l a n y i and Weissenberg, the two authors of the work on c e l l u l o s e . P o l a n y i was a t h e o r e t i c a l p h y s i c i s t and Weissenberg a mathematician so that the a d d i t i o n of a chemist to t h i s group was r a t h e r f a v o r a b l e . For work with the method of x-ray d i f f r a c t i o n two items were necessary: to study the theory and to l e a r n to work w i t h x-rays. So Mark s t u d i e d together with Weissenberg N i g g l i ' s book on c r y s t a l l o g r a p h y thoroughly. To work with s o f t x-rays, as i t i s necessary f o r d i f f r a c t i o n work, was r a t h e r d i f f i c u l t a t those times. X-Ray tubes f o r these purposes were not a v a i l a b l e comT
1
©
0097-615 6/ 81 /0175- 0021 $5.00/ 0 1981 American Chemical Society
Stahl; Polymer Science Overview ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
22
POLYMER SCIENCE OVERVIEW
m e r c i a l l y . One had to c o n s t r u c t the tubes o n e s e l f w i t h the help of a mechanic and a g l a s s blower. Tecause the x-ray tube was h a l f g l a s s and h a l f metal these m a t e r i a l s had to be compounded by means of a cement and, to keep up an e x c e l l e n t high vacuum, the tubes must be evacuated permanently during o p e r a t i o n . Anyway, t h i s was a j o b f o r a vacuum p h y s i c i s t and Mark was eager to l e a r n t h i s too. In 1922 Mark had j o i n e d the i n s t i t u t e i n B e r l i n and i n 1923 the f i r s t papers were published by him and h i s c o l l a b o r a t o r s (mostly students performing t h e i r d o c t o r a l t h e s i s ) . These papers concern the d e t e r m i n a t i o n of the c r y s t a l s t r u c t u r e s of Sn, SnJ^, urea (C0(NH )2), p e n t a e r y t h r i t o l (CCC^OH)^), hexamethylenetetramine (CgHi2.Nit)> * triphenylmethane (CH(CgH5)3). I t i s i n t e r e s t i n g to note that these papers had nothing to do w i t h work on f i b e r s or h i g h polymers a t a l l . This c h a r a c t e r i z e s the s i t u a t i o n a t that time. Only a few c r y s t a l s t r u c t u r e s were known and to perform s t r u c t u r a l work one had the c h o i c e . On the other hand one has to keep i n mind that the determination of a c r y s t a l s t r u c t u r e , at these times, was a d i f f i c u l t task. Because x-ray i n t e n s i t i e s of the s e l f - c o n s t r u c t ed x-ray tubes were r a t h e r low, the d i f f r a c t e d i n t e n s i t i e s had to be guessed from photographs. Hence, the only data which c o u l d be determined p r e c i s e l y from the l o c a t i o n of the spots or r i n g s on the photographs were the dimensions of the elementary c e l l . M i s s i n g r e f l e c t i o n s gave a h i n t on symmetry elements i n the c e l l and, by comparing them w i t h the symmetric s t r u c t u r e of the molecule of the i n v e s t i g a t e d substance, molecular and even atomic p o s i t i o n s could be guessed. For the guessed s t r u c t u r e x-ray i n t e n s i t i e s could be c a l c u l a t e d and from the agreement between guessed and c a l c u l a t e d i n t e n s i t i e s the degree of exactness of the determined s t r u c t u r e could be o b t a i n e d . But t h i s method was complicated because e l e c t r o n i c c a l c u l a t o r s were not a v a i l a b l e at that time. Consequently, many s t r u c t u r e determinations must be f i n i s h e d by having an idea of the symmetry of a s t r u c t u r e without being a b l e to g i v e exact atomic p o s i t i o n s . So, of the above-mentioned f i v e substances only the s t r u c t u r e s of t i n , urea and hexamethylene-tetramine could be determined up to the exact atomic p o s i t i o n s and t h a t , at those times, was extremely good. 2
Downloaded by CORNELL UNIV on July 20, 2016 | http://pubs.acs.org Publication Date: December 10, 1981 | doi: 10.1021/bk-1981-0175.ch002
a n c
The s i t u a t i o n i n the i n s t i t u t e changed f a v o r a b l y when a new b u i l d i n g was f i n i s h e d and a much b e t t e r x-ray l a b o r a t o r y was available. There was more space so that two x-ray tubes could be operated simultaneously and the time of o p e r a t i o n was extended from the morning up to almost midnight. Here, Mark, who had married meanwhile, got a f l a t i n the i n s t i t u t e . Often l a t e i n the evening Mrs. Mark came down to the l a b o r a t o r y w i t h some refreshments f o r those working i n the x-ray l a b o r a t o r y . Mark was v e r y popular and w e l l - l i k e d . Consequently, he always had many students and was i n the p o s i t i o n to s e l e c t the best ones to work w i t h him. So between 1922 and 1927, when he l e f t the i n s t i t u t e i n B e r l i n , 34 papers were p u b l i s h e d by him,
Stahl; Polymer Science Overview ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
2.
BRILL
23
Early Twenties
almost a l l of them together w i t h h i s students i n the frame o f a doctoral thesis. These papers concern simple substances l i k e Sn, C ( g r a p h i t e ) , S, N H 3 , C O 2 , (the l a s t two t e c h n i c a l l y d i f f i c u l t ) but a l s o more complicated organic substances l i k e hexamethylene-tetramine and many substances of the composition ABX^ as s u l f a t e s of many metals, ARi+ as C(CR^)i^ CiCI^OH)^ but a l s o high polymers l i k e c e l l u l o s e and 'Kautschuk . So i t was a l r e a d y at these e a r l y times evident that Mark was an extremely good s c i e n t i s t and, when he l e f t the i n s t i t u t e , he became a l i f e l o n g member of the K a i s e r - W i l h e l m - G e s e l l s c h a f t and i t s successor the Max-Planek-Gesellschaf t . 9
1
Downloaded by CORNELL UNIV on July 20, 2016 | http://pubs.acs.org Publication Date: December 10, 1981 | doi: 10.1021/bk-1981-0175.ch002
RECEIVED March 16, 1981.
Stahl; Polymer Science Overview ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
