354 CONSIDERATION OF CARBON COMPOUNDS. 



longer an acid reaction. Dissolve 1 gramme of the dry pyroxylin in a mixture 

 of 25 c.c. of ether and 8 c.c. of alcohol. The solution obtained is collodion. 



Gly cog-en, C 6 H 10 O 5 . Found exclusively in animals ; it occurs in 

 the liver, the white blood-corpuscles, in many embryonic tissues, and 

 in muscular tissue. Pure glycogen is a white, starch-like, amorphous 

 substance, soluble in water, insoluble in alcohol ; by the action of 

 dilute acids it is converted into glucose. 



Glucosides. This term is applied to a group of substances (chiefly 

 of vegetable origin) which, by the action of acids, alkalies, or fer- 

 ments, suffer decomposition in such a manner that one of the products 

 formed is grape-sugar. Glucosides may, therefore, be looked upon 

 as compound sugars, or sugar in combination with various other sub- 

 stances. The following is a list of the more important glucosides, 

 giving also their composition and the sources whence they are 

 obtained : 



Amygdalin, C 20 H 2r NO n Bitter almonds, etc 



Cathartic acid, C 180 H 19 ,N 4 SO 82 ? Senna. 



Carminic acid, C 17 H 18 O 10 Cochineal. 



Colocynthin, C 5 8H 84 O 23 ? Colocynthis. 



Digitalin, ? Digitalis 



Gentiopicrin, C 30 H 30 O 12 Root of gentiana. 



Glycyrrhizin, C 24 H 36 O 9 Liquorice root. 



. Helleborin, C 36 H 42 O 6 Root of hellebore. 



Indican, C 26 H 31 NO 17 Indigo plant. 



Myronic acid, C 10 H 19 NS 2 O 10 Seeds of black mustard. 



Salicin, C 13 H 18 O 7 Bark of willow. 



Tannins, C U H 10 O 9 In many barks, leaves, etc. 



Digitalin. The leaves of digitalis purpurea contain a number of glucosides, 

 mixtures of which in varying proportions form the official article sold under 

 above name. Digitonin is an amorphous, yellowish substance, soluble in 

 alcohol. Digitalein is a white, intensely bitter, amorphous substance. Digi- 

 toxin is a colorless, crystalline solid ; it is the most poisonous of the constituents 

 of digitalin, and is found in the leaves only to the extent of 0.01 to 0.02 per 

 cent. ; it is not a glucoside. Digitalin, (C 5 H 8 O 2 )#, is a white amorphous powder, 

 soluble at ordinary temperature in about 1000 parts of water and in about 100 

 parts of alcohol of 50 per cent. It is soluble in concentrated hydrochloric 

 acid, forming a golden yellow solution. A similar yellow solution is obtained 

 by dissolving it in concentrated sulphuric acid, the color gradually changing 

 to blood-red. The yellow color of the sulphuric acid solution changes to a 

 beautiful violet on the addition of a drop of nitric acid or ferric chloride. 



Myronic acid, C 10 H 19 NS 2 10 , is found as the potassium salt, which is known 

 as sinigrin, in black mustard seed. When treated with solution of myrosin, a 

 substance also contained in mustard seed and acting as a ferment upon myronic 



