THE URINE. 207 



XIII. DETERMINATION OF THE TOTAL SULPHUR AND OF THE 

 NEUTRAL SULPHUR. 



Fifty cubic centimeters of the urine, in the case of con- 

 centrated urines 25 cc., are evaporated in a platinum dish on 

 the water-bath to a small volume, 20 g. of nitrate mixture 

 (3 parts of saltpeter to 1 part of sodium carbonate) are 

 added and heated cautiously from the side till the mass fuses 

 ^completely and becomes white. On account of the sulphur 

 present in illuminating-gas a spirit-flame is preferable for the 

 heating. When cold dissolve the fused mass in water, rinse 

 it into a flask, and cautiously run into the flask, very gradu- 

 ,ally through a funnel, 100 cc. of hydrochloric acid. Then 

 heat on the sand-bath, with the funnel in the neck of the 

 flask, until the evolution of gas has completely ceased, place 

 in a porcelain dish, evaporate to dry ness, pour on 100 cc. of 

 hydrochloric acid, stirring thoroughly, again evaporate to 

 dryness, and repeat this operation once more. Take up the 

 dry residue with water, filter (to remove silicic acid) into a 

 beaker, heat on the wire gauze till boiling begins, and add 

 cautiously 10 cc. of hot barium chloride solution. Filter 

 next day, etc., as in the determination of the total sulphuric 

 .acid. 



By subtracting the amount of sulphur in the total sul- 

 phuric acid from the total sulphur we obtain the neutral 

 .sulphur. 



XIV. DETERMINATION OF ETHEREAL SULPHURIC ACID. 



For this determination it is best to use urine voided after 

 the use of phenol or the urine of persons suffering with ileus. 



Mix equal volumes (75 or 100 cc.) of urine and alkaline 

 barium chloride solution (mixture of two volumes of baryta- 

 water and one volume of barium chloride solution) in a dry 

 beaker, stir thoroughly, and filter after a few minutes through 



