DETECTION OF PROXIMATE PEIXCIPLES 135 



6. If albumin or globulin is absent : — 



(a) Neutralisation causes a precipitate soluble in excess of weak acid or 

 alkali. Acid albnmiii or alkali albnnun, according as the reaction of the 

 original liquid is acid or alkaline respectively. If the original -liquid is 

 neutral, acid albumin and alkali albumin must be both absent. 



(6) NeutraUsation produces no such precipitate : Proteose or peptone. 



7. If proteose, or peptone, or both, are present, saturate a fresh portion 

 with ammonium sulphate : 



(a) Precipitate : Proteose, (b) No precipitat-e : Peptone. 

 If both are present, the precipitate contains the proteose, and the filtrate 

 the peptone. 



8. To a fresh portion add nitric acid (proteids having been proved to be 

 present). 



(a) No precipitate, even though excess of soditmi chloride be also added : 

 Peptone. 



(b) No precipitate, until excess of sodium chloride is added : Dentero- 

 proteose. 



(c) Precipitate which disappears on heating and reappears on cooUng : 

 Proteoses. This is the distinctive test of all the proteoses or albxmioses, and 

 is given by all of them. For one of them, however (deutero-proteose), excess 

 of sodium chloride must be added also. 



(d) Precipitate Uttle altered by heating : Albnmin or globulin. 



In all four cases nitric acid plus heat causes a yellow colour, tamed orange 

 by ammonia. 



9. Confirmatory tests for proteids : — 

 (a) Millon's test. 



(6) Ferrocyanide of potassium and acetic acid causes a precipitate (except 

 in the case of peptones and some proteoses). 



(c) To test for fibrinogen : — 



i. It coagulates by heat at 56° C. 



u. It is changed into fibrin by fibrin ferment and calcium chloride. 



(d) To test for caseinogen : — 

 i. It is not coagulated by heat. 



ii. It is changed into casein by rennet and calcium chloride. 



10. If blood is suspected — 



(a) Examine spectroscopically, diluting if necessary. 



i. Oxyhaemoglobin shows two bands between D and E. 



ii. Add ammonium sulphide ; one band only appears. 



iii. Carbonic oxide hsemoglobin shows two bands also, but will not reduce 

 with anunonium sulphide. 



iv. Methaemoglobin gives a typical band in the red between C and D. 



v. Hsematin &c. show special spectra (see Advanced Course). 



(6) Dry : boil with glacial acetic acid and a crystal of sodium chloride on 

 a glass slide under a cover glass. Heemin crystals are obtained. 



