162 PYROTARTARIC ACID. 



2. Isosuccinic acid, CIP.CH j QQ QJJ 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. The sodium salt gives no precipitate with 

 iron chloride. 



4. Pyrotartaric Acid. 



OTTO* - C3H I Ca H - CH3 - CTLCa011 

 ( CO.OH CH 2 .CO.OH. 



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, citra- 

 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 solution 

 in the presence of a salt of uranium in direct sunlight 

 into carbonic anhydride and butyric acid. 



Its salts are crystallizable and almost all soluble in 

 water. The acid potassium salt C 5 H 6 O.HK and the 

 neutral calcium salt C 5 H 6 4 Ca + 2H 2 are difficultly 

 soluble; the silver salt C 5 II 6 4 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 are somewhat 

 different from each other ; they have been designated, 



