346 Mr. T. J. Herapath on the Combination of 



boiling water ; care being taken to reduce the compound to a 

 still more minute state of division, by patient trituration in a 

 mortar, after each digestion, &c, The washings, on being treated 

 by Rcinsch^s process, were found to contain a large propoi-tion 

 of arsenious acid. 



The insoluble residue having been digested in water for about 

 twelve or fifteen hours, as before described, was dried and weighed. 

 It amounted to about 29 grs.* It was then boiled in strong 

 hydrochloric acid, when it dissolved with the characteristic 

 colour of the proteine compounds. Upon testing this solution in 

 the usual manner, only exceedingly minute traces of arsenic 

 could be detected ; a quantity insufficient to yield, on oxidation, 

 a perceptible sublimate of arsenious acid. 



Eocperiment II. — According to the authorities above referred to, 

 61*07 grms. of albumen will combine with 0'38Ggrm. of arsenious 

 acid =0*G32 per cent. If this statement be correct, I argued, of 

 course if I make a mixture of these two substances, so arranging 

 my experiment that the arsenious acid shall not be present in such 

 large quantity, or in other words, if I employ an excess of albu- 

 men, and evaporate the compound to dryness, no trace of ar- 

 senious acid ought to be extracted from the mass upon subse- 

 quent digestion in boiling water. 438*5 grs. of glairy albumen 

 were therefore mixed with an aqueous solution of arsenious acid, 

 containing 0*25 gr. of AsO"^. The mixture was evaporated to 

 dryness in a gas-oven, and the brittle residue thus obtained 

 treated as in the preceding experiment. The washings, when 

 tested by Reinsch^s process, gave evident tokens of the presence 

 of a large quantity of arsenic. The insoluble residue, however, 

 when decomposed in the usual manner by sulphuric acid and 

 heat, and afterwards introduced into Marshes apparatus, gave 

 but very faint stains of metallic arsenic. 



Escperiments III., IV, and V. — The same experiments repeated, 

 different proportions of arsenious acid and albumen only being 

 employed. Similar results were obtained. 



Experiment VI, — Experiment II. repeated, the same quan- 

 tities of arsenious acid and albumen being used. Instead of 

 evaporating the mixture to diyness, however, as before, it was 

 merely heated to the boiling-point and then filtered, in order to 

 separate the coagulum which was formed. This latter was then 

 divided into two portions ; one of these was treated by Reinsch's 

 process, and found to contain sensible quantities of arsenic, as 

 did also the liquid from which the coagulate had been separated, 

 in cither case bright steel-gray stains being formed upon the 



* It must be understood, however, that this quantity does not represent 

 the whole of the albumen contained in the white of egg employed; a por- 

 tion was undoubtedly lost during the long-continued washing. 



