298 



PHYSIOLOGICAL CHEMISTRY. 



FIG. 95. 



which has been separated from the ethereal sulphates and has com- 

 bined with the barium of the BaCl 2 to form BaSO 4 . 



3. Detection of Loosely Combined or Neutral Sulphur. 

 Place about 10 c.c. of urine in a test-tube, introduce a small piece of 

 zinc, add sufficient hydrochloric acid to cause a gentle evolution of 

 hydrogen and over the mouth of the tube place a filter paper satu- 

 rated with plumbic acetate solution. In a short time the portion of 

 the paper in contact with the vapors within the test-tube becomes 

 blackened due to the formation of lead sulphide. The nascent 

 hydrogen has reacted with the loosely combined or neutral sulphur 



to form hydrogen sulphide and this 

 gas coming in contact with the plum- 

 bic acetate paper has caused the 

 production of the black lead sulphide. 

 Sulphur in the form of inorganic 

 or ethereal sulphuric acid does not 

 respond to this test. 



4. Calcium Sulphate Crystals. 

 Place 10 c.c. of urine in a test- 

 tube, add 10 drops of calcium chlo- 

 ride solution and allow the tube to 

 stand until crystals form. Examine 

 the calcium sulphate crystals under the microscope and compare 

 them with those shown in Fig. 95, above. 



Chlorides. 



Next to urea, the chlorides constitute the chief solid constituent 

 of the urine. The principal chlorides found in the urine are those 

 of sodium, potassium, ammonium and magnesium, with sodium 

 chloride predominating. The excretion of chlorides is dependent, 

 in great part, upon the nature of the diet, but on the average the 

 daily output is about 10-15 grams, expressed as sodium chloride. 

 Copious water-drinking increases the output of chlorides consider- 

 ably. Because of their solubility, chlorides are never found in the 

 urinary sediment. 



Since the amount of chlorides excreted in the urine is due pri- 

 marily to the chloride content of the food ingested, it follows that 

 a decrease in the amount of ingested chloride will likewise cause a 

 decrease in the chloride content of the urine. In cases of actual 

 fasting the chloride content of the urine may be decreased to a 

 slight trace which is derived from the body fluids and tissues. 



CALCIUM SULPHATE. 

 and Weil.} 



(Hensel 



