308 CHEMISTRY OF THE PROTEIDS CHAI 



2. The second type of coagulation is seen if one uses coppe 

 sulphate. It resembles ZnS0 4 in also giving a precipitate in ver 

 dilute solutions (O'OOOS to O'OOl normal), and giving no precipitat 

 in normal solutions, 1 but it differs from ZnS0 4 in giving with 1 : 1 

 egg-white a secondary precipitate even if used in strengths of si 

 times normal, Galeotti has, however, shown that copper sulphat 

 with very high concentrations of albumin behaves as follows : " 

 dissolving a large amount of copper albuminate in a supersaturate 

 CuS0 4 -solution and inspissating the fluid under a bell-jar with som 

 H 2 S0 4 , one obtains at first only crystals and the solution remain 

 clear, but gradually as the crystals increase in size, the fluid become 

 turbid and a more or less abundant precipitate of albumin settle 

 down." To dissolve this precipitated albumin it is necessary to dilut 

 the original solution with more saturated copper sulphate solution, a 

 addition of mere water leads to a further precipitation of albumin. 



Copper sulphate is thus characterised by giving precipitates on! 

 in feeble concentrations, and by dissolving the precipitate, forme 

 originally, whenever its concentration amounts to more than 1 norma 



3. The third type is represented by silver nitrate, which pre 

 cipitates in all strengths from O'l to 6 normal (Pauli), but if exces 

 of albumin be present large amounts of the silver-albumin-compoun< 

 are redissolved (Galeotti). 



Corrosive sublimate seems to the author to belong to the thin 

 type. Rose, 2 however, has pointed out that haemoglobin prepared b; 

 Berzelius' method is precipitated by concentrated sublimate, but tha 

 on diluting the mixture it passes into solution, to be, however, repre 

 cipitated by increasing the amount of sublimate. The author in hi 

 Physiological Histology was the first to make experiments to determin 

 the antagonistic effects produced by sodium chloride on the precipita 

 tion of egg-white by corrosive sublimate, for this question is of grea 

 importance in connection with the fixing of tissues for histologies 

 purposes, the medicinal application of sublimate and the sterilisatiol 

 of hands and wounds by sublimate. He based his explanation on tb 

 electro-affinity of metals (see footnote, p. 313). 



The following experiments are taken from the author's Physiologiea 

 Histology, pp. 109-113. 



EXPERIMENT 8 A 



In the first experiment 5 per cent watery solutions of sublimat< 

 and of common salt were used in the amounts stated in the table 



1 The molecular weights of ZnS0 4 and CuS0 4 are 160'9 and 159 '2. 

 2 F. Rose, Poggendorfs Annalen, 28. 132 (1833). 



