81 



Euplirasia Tannic Aci<l=C32 Hoo On. Peculiar tannic acid 

 of Euphrasia officinalis, greening the iron salts, and only obtained 

 in combination with lead; precipitable by glue and by tartarated 

 antimony. 



Evernic Acid = 034 Hie O14. Besides Usnic acid in Evernia 

 })i-unastri. Precipitate the extract of the lichen, pre])ai-ed 

 with diluted milk of lime, 'with hydrochloric acid and boil the 

 deposit with weak alcohol; or dry and exhaust with ether. The 

 solution of the E. is purified by recrystallisation under aid of 

 animal charcoal. — Colourless crystalline needles, inodorous and 

 tasteless, of acid reaction; lose at 100° nothing of their weight; 

 fuse at about 164°; are afterwards decomposed and yield beside 

 other products a sublimate of orcin; are insoluble in cold and 

 dissolve slightly in boiling water, also in cold and very abundantly 

 in hot alcohol ; readily in ether, also in alkalies, the solution in 

 ammonia turning slowly to a deep-red by exposure to the air. 



Extractive Substances. By extracting vegetable matters with 

 water or alcohol, a more or less yellow or brown liquid is obtained 

 which becomes darker on evaporating under the influence of the 

 air, and remains as a stiff pasty mass difficult to dry and quickly 

 absorbing moisture when exposed to the air. This product has the 

 general name of extract, and represents a mixture of the most 

 difierent matters and salts of the plant employed. The general 

 characteristics of extracts are as follows: solubility in water and 

 alcohol, insolubility in ether, amorphous condition, non-volatility, 

 hygroscopicity, and finally inclination to decompose when in 

 solution under concuiTence of heat and air. Among the substances 

 common to all extracts are gum, sugar, pigments, salts, &g., 

 because they are soluble in water and alcohol, and are accordingly 

 canied into the extracts. In cases where one or the other of the 

 aforesaid sirbstances predominates and in default of sufficiently 

 accurate analysis, or when no mode of isolation is known, the 

 remaining mixture, called extract, is spoken of and designated 

 according to its predominating character, as bitter, sweet, astiin- 

 gent, gummous, colouring, resinous, &c., extractive substance. 



It follows therefore that the name "extractive substance" does 

 not mean a well-defined body, but comprises a mixture of sub- 

 stances, which advancing knowledge will teach to separate. 



Fats. Non- volatile compounds of carbon with hydrogen and 

 comparatively little oxygen; widely distributed throughout the 

 vegetable empire, and most abundantly occurring in seeds; at a 

 mean temperature of all consistencies from that of an oil to a solid ; 

 colourless or yellowish, with a greenish or brownish shade ; of im- 

 perceptible or faint odour and taste; leave a permanent spot on 

 paper, are lighter than water (spec. grav. between 0-88 and 0-95); 

 the solid fats fuse almost without exception below 100°; not in- 



