172 ESSENTIALS OF CHEMICAL PHYSIOLOGY 



6. If proteins are present, but albumin or globulin absent : 



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

 alkali. Acid albumin or alkali albumin, 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. 



(b) Neutralisation 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 precipitate : Peptone. 

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

 the peptone. 



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

 present). 



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

 Peptone. 



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

 proteose. 



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

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

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

 of sodium chloride must be added also. 



(d) Precipitate little altered by heating: Albumin or globulin. 



In all four cases nitric aeidplus heat causes a yellow colour, turned orange 

 by ammonia (xantho-proteic reaction). 



9. Confirmatory tests for proteins : 



(a) Millon's test (see p. 27). 



(b) Adamkiewicz's reaction (see p. 27). 



(c) Ferrocyanide of potassium and acetic acid cause a precipitate (except 

 in the case of peptones and some proteoses). 



(d) To test for fibrinogen : 



i. It coagulates by heat at 56 C. 



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



(e) 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. 



11. Add ammonium sulphide ; one band only appears. 



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

 with ammonium sulphide. 



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



v. Haematin, &c., show special spectra (see Advanced Course, Lesson XIX.). 



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

 a glass slide under a cover glass. When cold, haernin crystals are seen. 



