136 ESSENTIALS OF CHEMICAL PHYSIOLOGY 



(c) If the blood is old and dry, and its haemoglobin converted into 

 hsematin. 



i. Try hsemin test. 



ii. Dissolve it in potash ; add ammonium sulphide, and examine for 

 spectrum of haemochromogen. 



11. If bile is suspected. 



(a) Try Gmelin's test for bile pigments. This is the test for bile in urine, 



(b) Try Pettenkofer's test for bile salts. 



12. Miscellaneous substances : 



(a) Mucin. Precipitated by acetic acid or by alcohol. The precipitate is 

 soluble in lime water. By collecting the precipitate and boiling it with 25- 

 per-cent. sulphuric acid, a reducing sugar is obtained. Mucin gives the 

 proteid colour tests. 



(b) Nacleo-proteid. — Precipitated by acetic acid or by alcohol. The pre- 

 cipitate is often viscous. It is soluble in dilute alkalis like 1 per cent, sodium 

 carbonate. This solution causes intra-vascular clotting. If the precipitate 

 is collected and subjected to gastric digestion, an insoluble deposit of nucleia 

 is left, which is rich in phosphorus. Nucleo-proteid gives the proteid colour 

 tests. 



(c) Gelatin. This also gives the proteid colour tests. It is not coagulated, 

 but dissolved in hot water. The solution gelatinises when cold. 



{d) Urea. Very soluble in water. The solution effervesces when sodium 

 hypobromite or fuming nitric acid is added. Concentrate a fresh portion, 

 add nitric acid, and examine for crystals of urea nitrate. Solid urea heated 

 in a dry test-tube gives off ammonia, and the residue is called biuret. This 

 gives a rose-red colour with copper sulphate and caustic potash. 



(e) Uric acid. Very insoluble in water ; soluble in potash, and precipitated 

 from this solution in crystals by hydrochloric acid. Uric acid crystals from 

 human urine are deeply pigmented red. Try murexide test. 



(/) Cholesterin. Characteristic flat crystalline plates. Play of colours 

 with iodine and concentrated sulphuric acid. 



13. Urine. Normal constituents : 



(a) Chlorides. Acidulate with nitric acid ; add silver nitrate ; white 

 precipitate. 



(fe) Sulphates. Acidulate with nitric or hydrochloric acid : add barium 

 chloride ; white precipitate. 



(c) Phosphates, Acidulate with nitric acid ; add ammonivma molybdate ; 

 boil ; and a yellow crystalhne precipitate forms. To another portion add 

 ammonia ; earthy (i.e. calcium and magnesivim) phosphates are precipitated. 



(d) Urea (see above). 



(e) Uric acid. To 100 c.c. of urine add 5 c.c. of hydrochloric acid ; leave 

 for twenty-four hours, and pigmented crystals of uric acid are formed, l^or 

 tests see above. 



if) Hippuric acid. Evaporate the urine with nitric acid, and heat the 

 residue in a dry test-tube. A smell of oil of bitter almonds is given off. 

 ig) Creatinine. Take 100 c.c. of urine : add 5 c.c. of a saturated solution 



