FERMENTS AND MISCELLANEOUS PRODUCTS 89 



acids it is resolved into glucose and saliginin (O. oxybenzyl 

 alcohol). 



Ci 3 H 18 7 + H 2 -> C 6 H 12 6 + C 6 H 4 (OH)CH 2 OH 



(Salicin.) (Glucose.) (Saliginin.) 



It has been prepared synthetically, and its constitution and 

 that of other glucosides of saliginin are given as follows : 



(Salicin.) (Populin.) 



(Helicin.) 



% 



Arbutin, on hydrolysis, yields glucose and hydroquinone 

 (dihydroxybenzene). 



Ci 2 H 16 7 + H 2 -> C 6 H 12 6 + C 6 H 4 (OH) 2 



(Arbutin.) (Glucose.) (Hydroquinone.) 



Potassium myronate, which occurs in the seeds of both the 

 .black and white mustard, is resolved by acids and by ferments 

 into potassium hydrogen sulphate, glucose and mustard oil 

 (allylisothiocyanate). 



C 10 H 18 NS 2 10 K - C 6 H 12 6 + C 3 H 5 NCS + KHSO 4 



(Pot. myronate.) (Glucose.) (Mustard oil.) 



Tannins. The name * tannin " was originally given to the 

 compound found in the aqueous extract of oak bark which 

 is used in the process of tanning hides. It has since been 

 extended to a large number of substances of a more or less 

 similar character which are widely distributed in the vegetable 

 kingdom. They occur in quinine bark, tea leaves, coffee 

 beans, beech nuts, etc. These are called physiological tannins 

 in contradistinction to the pathological product found in oak 

 galls to the extent of 50 per cent. 



The tannins are all soluble in water and have a bitter, 

 astringent taste. They give a very dark blue or green colora- 

 tion (ink) with ferric salts, and are precipitated by neutral 

 solutions of lead acetate. They precipitate the soluble 



