OF ARTS AND SCIENCES. 195 



trated acid the decomposition is far from complete. After boiling for 

 some time with acid of Sp. Gr. 1.20, and evaporation upon the water- 

 bath, fumaric acid was obtained, together with small quantities of oxalic 

 acid. The fumaric acid was identified, as before, by its physical prop- 

 erties, and by an analysis of its silver salt. 



0.1508 grm. of the salt dried at 125° gave 0.1710 grm. AgBr. 



Calculated for 

 Ag 2 C 4 II 2 4 . Found. 



Ag 65.46 65.15 



The reaction with concentrated nitric acid is much more interesting, 

 since the sulpho-group is in this way replaced by the nitro-group and 

 the 8-nitropyromucic acid of Klinkhardt,* formed with comparatively 

 little oxidation. This replacement is slowly effected at ordinary tem- 

 peratures, but rapidly at 100°. Dry sulphopyromucic acid is slowly 

 added to several times its weight of cold fuming nitric acid. The 

 mixture is at first cooled, and the reaction afterward completed by 

 gentle heat. The nitric acid is then partially removed by evaporation, 

 and the nitropyromucic acid, which separates as the solution cools, re- 

 crystallized from hot water. For its complete purification we found it 

 necessary to dissolve the acid in a cold dilute solution of sodic carbon- 

 ate, to extract with ether this alkaline solution, and to recrystallize 

 from hot water the product obtained by the addition of hydrochloric 

 acid. The pale yellow acid thus obtained crystallized in rectangular 

 plates, which melted at 182-183°. 



0.4925 grm. substance gave 37.9 c. c. of moist nitrogen at 16° and 

 under a pressure of 748 mm. 



Calculated for 



C H 3 (N02)0 3 . Found. 



N 8.91 8.82 



The ethyl ether of the acid was easily formed by warming its alco- 

 holic solution with concentrated sulphuric acid. It was sparingly sol- 

 uble in cold alcohol, and crystallized in broad lustrous plates, which 

 melted at 99-100°. Klinkhardt gives the melting-point of the acid 

 as 183°, and of the ether as 101°. 



With the S-nitropyromucic acid is formed in small quantity a neutral 

 substance containing nitrogen, which was obtained by evaporating the 

 ether used in the extraction of the alkaline solution of the crude nitro- 



* Journ. pr. Chemie N. F., xxv. 41. 



