BUTYRIC ACIDS. 93 



wood. Its ethyl ether is produced together with other 

 substances by the successive action of sodium and ethyl 

 iodide on acetic ether (p. 82). Most readily obtained by 

 the fermentation of sugar. 3 kilogrammes cane-sugar 

 and 15 grm. tartaric acid are dissolved in 13 kilogrammes 

 boiling water and allowed to stand for a few days ; 

 then about 120 grm. rotten cheese, suspended in 4 kilo 

 grammes sour milk, and 1 J kilogrammes chalk, are added, 

 and the whole allowed to remain unmolested in some 

 place, where the temperature is kept at 30-35. In 

 ten days the mass becomes pulpy from the presence of 

 calcium lactate, which has separated ; at a later period 

 hydrogen is evolved together with carbonic anhydride, 

 the mass again becomes a thin liquid, and in the course 

 of five or six weeks the fermentation is completed. Now 

 the same volume of water and 4 kilogrammes crystal 

 lized sodium -carbonate are added, the calcium carbo 

 nate filtered off, the filtrate evaporated to about 5 kilo 

 grammes, and then mixed with 2} kilogrammes sul 

 phuric acid previously diluted with water. The prin 

 cipal amount of butyric acid separates as an oily layer. 

 It is removed, desiccated by means of calcium, chloride 

 and then rectified. By distilling the residual solution 

 of the salt, the dissolved acid can be obtained from this. 



Colorless liquid, boiling at 157 ; specific gravity, 

 0.988 at ; mixes with water in every proportion; is, 

 however, thrown down from its watery solution by 

 easily soluble salts. It is not acted upon by potassium 

 bichromate and sulphuric acid ; by continued oxidizing 

 with nitric acid, a small portion is converted into suc- 

 cinic acid. 



Its salts are soluble in water. 



Calcium butyrate, (C 4 IF0 2 ) 2 Ca, is less soluble in 

 hot water than in cold. A solution, saturated at the 

 ordinary temperature, on being heated, throws down 

 nearly all the dissolved salt, in the form of lustrous 

 laminae. 



Silver butyrate, C 4 H 7 2 Ag, crystallizes from hot 

 water in microscopic prisms. 



