Intelligence and Miscellaneous Articles. 491 



nia also possesses the property of combining atom to atom with the 

 earthy ferrocyanides. — L'Institut, August, 1839. 



PURPURIC ACID. 

 M. Fritzche in January last, read before the Academy of Sciences 

 of St. Petersburgh a notice respecting purpuric acid and its salts. 



It is not long since that the name of purpuric acid was given to 

 a substance discovered by Prout, which had neither a purple colour, 

 nor possessed acid properties, but it was so named, because it was 

 extracted, by means of an acid, from purpurate of ammonia*. The re- 

 searches of Liebig and Wohler on the products of the decomposition 

 of uric acid by nitric acid, have proved that this substance is the 

 product of the complete decomposition which purpurate of ammonia 

 undergoes by most acids, and they have consequently given it the very 

 proper name of murexane ; but this is not the case with the new 

 name of murexide, which these chemists have applied to purpurate 

 of ammonia on account of its not being a salt but an amide. This 

 principle could be correct if only one ammoniacal body could be 

 thus formed; but in the year 1818, Prout had shown that a great 

 number of other purpurates could be obtained with the purpurate 

 of ammonia; and soon afterwards Vauquelin described the pro- 

 l)erties of purpurate of silver : more lately Kodweis analysed the pur- 

 purate of barytes ; and from this period the purpurates are described 

 in all treatises on chemistry, although the composition of purpuric 

 acid is unknown, and it was known only that it transformed am- 

 moniacal salts into another class of substances. The memoir of M. 

 Fritzche has for its object the reestablishment of the name of pur- 

 puric acid, to prove that it really exists as an acid in the salts which 

 have been called purpurates, which is known only in combination 

 with bases, to analyse the purpurates, and to supply the deficiencies 

 which still exist as to our knowledge of the compounds which this acid 

 may form. The following are the results obtained by M. Fritzche. 

 Purpuric acid has not yet been isolated ; when attempts are made 

 to separate it from its combinations by means of acids, it is decom- 

 posed, and yields, in dilute solutions, principally murexane, whereas 

 with concentrated solutions it forms other products. Purpuric acid 

 forms with bases, salts which are slightly soluble, and remarkable 

 for the fine purple colour of their solutions. Besides these neutral 

 salts, in which the base is to the acid as 1 to 10, it forms basic salts 

 also, but not acid salts. When perfectly free from water, pur- 

 puric acid consists of 



Hydrogen 1-581 = H« 



Carbon 38-725 = C'^ 



Oxygen 31-665 = Qio 



Azote .... 28-029 = N'o 



100- 



* This is not correctly stated. Although purpurate of ammonia had been 

 long known, it did not receive that name until after Dr. Prout had obtained 

 the acid from it, which, at the suggestion of Dr. Wollaston, from its forming 

 purple salts, he then called purpuric acid. See Phil. Trans, for 1818, or 

 Phil. Mag., First Series, vol. liii. p. 25. — Edit. 



