96 PHYSIOLOGICAL CHEMISTRY. 



This is a substance made by the partial digestion of fibrin, gel- 

 atin, serum and other bodies and is not uniform or homoge- 

 neous in structure. It contains representatives of the several 

 classes of derived digestion products. 



Ex. Dissolve about 5 gm. of commercial peptone in 50 cc. of water 

 and use small portions of the solution for these tests : To one portion 

 add some strong nitric acid ; this produces a precipitate. To a second por- 

 tion add a little copper sulphate solution, which gives a light greenish 

 precipitate. To a third portion add a few drops of acetic acid and then 

 some potassium ferrocyanide. This makes a turbidity or may even cause 

 a precipitate. Now to the remaining and large portion of the original 

 solution add an equal volume of a saturated solution of ammonium sul- 

 phate. A marked precipitate of primary albumose separates and may be 

 filtered off after a time. When the liquid has all passed through the filter 

 note that the precipitate may be easily dissolved by adding fresh water, 

 and further that this new solution is not coagulated by boiling. Note also 

 that the solution gives a good biuret reaction. 



Ex. Use the filtrate from the primary albumose precipitate for a further 

 test. Add to it powdered ammonium sulphate to complete saturation, that 

 is, as long as the powder dissolves on thorough shaking. Then add five 

 to ten drops of a weakly acid solution of ammonium sulphate (which may 

 be obtained by adding to 10 cc. of saturated ammonium sulphate solution 

 five drops of concentrated sulphuric acid). This last treatment with the 

 acid ammonium sulphate gives a new albumose precipitate which after a 

 time may be separated by filtration. Save the filtrate and test the pre- 

 cipitate as follows : Dissolve it in fresh water and test portions with copper 

 sulphate, nitric ?cid and the potassium ferrocyanide. These reagents gave 

 precipitates with the original peptone solution, but yield nothing with the 

 solution of the new albumose, which is called secondary albumose. 



Ex. The filtrate from the secondary albumose may finally be tested. 

 Add to it an excess of concentrated sodium hydroxide solution and then 

 a drop of dilute copper sulphate solution. This gives a purple red biuret 

 color, showing the presence of a soluble product not precipitated by am- 

 monium sulphate in excess. This soluble product is the peptone, repre- 

 senting the last stage of the true digestion. This peptone gives no pre- 

 cipitation reactions with the reagent used above. 



The first of these fractions, or the primary albumoses, may 

 be converted by further acid treatment or by digestion into 

 secondary albumoses no longer precipitated by half saturated 

 ammonium sulphate. By solution in water and addition of 

 alcohol it is possible to separate this primary albumose into 

 two sub-fractions which are pretty well characterized. The 



