1891.] A New Test for Albumin and other Proteids. 373 



When the peptone was removed by precipitation with excess of 

 alcohol and filtration, the remaining fluid failed to give the slightest 

 proteid reaction with salicyl-sulphonic acid. 



It will be noticed that there is an important difference in the be- 

 haviour of proteoses and peptones as compared with the other proteid 

 bodies under the influence of the salicyl-sulphonic acid ; the pre- 

 cipitate yielded by the proteoses and peptones clears up on heating, 

 and reappears on cooling, while the precipitate of the other proteids 

 does not clear up on heating, but, on the other hand, becomes 

 markedly flocculent. In this respect the reagent resembles picric 

 acid and mercuro-potassic iodide, and to some extent also nitric acid. 

 It differs from the latter, however, inasmuch as the latter gives no 

 ipitate with peptones. 



s regards the nature of the precipitate of egg albumin, or 

 urn albumin, thrown down by salicyl-snlphonic acid, its general 

 appearance might suggest that not only precipitation, but also 

 coagulation, had occurred, as with nitric acid, &c. But the fact that 

 is soluble on the addition of a sufficiently large amount of a very 

 ,k solution of potassic hydrate (O'l per cent.) or of sodium car- 

 mate (1 per cent.) shows that no coagulation could have taken place. 

 Solution of the precipitate does not take place as long as any acidity 

 remains in the fluid. And when it has been redissolved the addition 

 of a very small amount of a weak acid (nitric, acetic, sulphuric) can 

 again bring about precipitation. 



The precipitate of albumin thrown down by salicyl-sulphonic acid 

 ot redissolved by the addition of even considerable amounts of 

 acid, nor is it dissolved by nitric acid, except when a large 

 iunt of the strong acid is added. 



hen salicyl-sulphonic acid is made to act upon albumin for some 

 me, especially at a high temperature, and the precipitate is then 

 itered off, the filtrate shows a very marked coloration, varying from 

 inkish tint to a bright amethyst. The filter paper commonly 

 .ows a staining of the same colour. When the fluid is filtered hot, 

 the filtrate usually shows evidence of containing albumoses; it 

 mes turbid on cooling, and clears up on heating. The colora- 

 n of the filtrate is most marked and pure when the fluid is clear 

 ., when hot) ; when it is turbid the colour is, to some extent, 

 :ed and modified (often to an orange-pink tint) by the presence 

 the precipitate. 



II. On the use of Salicyl-sulplionic Acid as a Test for Proteids in 



Urine. 



Jalicyl-sulphonic acid gives no precipitate whatever with normal 

 ic. 



