162 PYROTARTARIC ACID. 



2. Isosuccinic acid, CIP.CII j QQJJ is formed 



by heating cyanpropionic acid with alkalies. The 

 ethyl ether is formed by boiling formic and lactic 

 ethers with phosphoric anhydride. Crystals, fusing at 

 130; sublimes below 100 ; but, when heated to 150, 

 is resolved into propionic acid and carbonic anhydride. 

 It is more easily soluble in water (in 5 parts), than 

 succinic acid. Tne sodium salt gives no precipitate with 

 iron chloride. 



4. Pyrotartaric Aci<L 



caon - CIP.CII.CO.OII 

 CO.OII - 6tt.CO.OIL 



Formation. By^ dry distillation of tartaric acid (best 

 when the acid is previously mixed with an equal 

 weight of pumice-stone) and evaporation of the distil- 

 late to crystallization ; or by heating with concentrated 

 hydrochloric acid at 180 ; from propylene cyanide by 

 heating with acids or potassa; from itaconic, eitni- 

 conic, and mesaconic acids by the action of nascent 

 hydrogen ; from gamboge by fusing with potassa. 



Properties. Small, transparent crystals, which fuse at 

 112 and decompose partially at a higher temperature 

 into water and the anhydride. Easily soluble in water, 

 alcohol, and ether. Decomposes in an aqueous solut i< n 

 in the presence of a salt of uranium in direct sunlight 

 into carbonic anhydride and butyric acid. 



Its salts are crystallizablc and almost all soluble in 

 water. The acid potassium salt C 5 IP0 4 .HK and the 

 neutral calcium salt OIPCK/a + 2IPO are difficultly 

 soluble; the silver salt C'IPO'Ag 2 is an insoluble, 

 white, curdy precipitate. 



The substitution-products of pyrotartaric acid are 

 formed by direct addition of chlorine, bromine, or 

 hydrogen acids to itaconic acid and the isomeric citra- 

 conic, and mesaconic acids. The substitution-products 

 obtained in this way from these acids arc somewhat 

 diUcrcnt from each other; thuy liave been designated, 



