s^ Ni'iii-'.sis ()!•- i)i:i"si))i.s. 145 



case wen- liiiiiti'd to iIr- taiiiiin of ^all apples and some suhstaiiccs 

 which belong to the same type. The tirst e.\])eriTiieiits carried 

 out by Fischer and Freudenberj:^ had for their object the (|Uestion 

 whether the glucose, lirst observed by' Strecker in 1S5J-4. was in 

 reality a coni])onent of the tannin molecule or merely an acci- 

 dental adulteration. {"or this ])ur])ose the\- used as raw 

 materials : — 



(a) Acidum tannicum le\iss. puriss. (.Merck's purest prepara- 

 tion); {b) ditto (Kahlbaum), both of which they subjected to 

 purification by special methods devised for this j)ur])ose. Briefly 

 these consisted in {a) extraction with ether, which gave a yield 

 of 60 per cent.; {b) extraction with ethyl acetate gave a viel'd of 

 60 per cent. ; \ c) prej^aration of the ])otassium salt and subsecpient 

 acidification with N.fL,SOjAc|. 



The object was to get a preparation as pvux" as it was pos- 

 sible to get. 'J'he purified tannin so prepared was so hygroscopic 

 that great care had to be taken to exclude the moisture of the 

 atmosphere when weighing. On analysis the following numbers 

 were obtained : — 



I. 



Carbon, \mr cent 53-^ 



H\drogen. per cent. ... 3.25 



I. Merck's tanuin i)urihed by method /'. 



II. Kahlbaum's ditto. 



III. Kahlbaum's tannin i)urified by method c. 



IV. Kahlbaum's tannin, not purified, but dissolved out with 

 water. 



V. Merck's tannin })urified by method a. 



The optical rotatory power was also determined, and gave 

 for three dift'erent i)rei)arations of I the values 



•2 

 [a] =+62.65° (+2'') A([ueous solutions. 



+70.09° (+1°) 



+ 18.43° (+3°) Alcoholic solution. 



for two different preparations of III the values 



2 1) 

 i^] +70.77° (.+2° ) Aqueous solutions. 



+68.48° (4^2°) 

 and for V +58.23° (+2°). 



Theoretically — 



Digallic Acid contains C. 52. 16 ^r H. 3. 13 % 



Pentagalloyl glucose C. 52. 33 7' H.3.43% 



Pentadigalloyl glucose <-o3-63 7 H.3.08^ 



These analyses did not lead to any definite conclusion. The 

 acidity was next tested and found to be one-tenth that of gallic 

 acid. 



