TOTAL SULPHATES 73 



TOTAL SULPHATES 



Folin's Method 1 



Principle. The sulphuric acid of the conjugated sulphates is 

 set free by boiling with acid. The total sulphates are then pre- 

 cipitated with barium chloride. 



Procedure. Place 25 c.c. of urine in a 200 to 250 c.c. Erlen- 

 meyer flask, add 20 c.c. of dilute hydrochloric acid (1 volume of 

 concentrated HC1 to 4 volumes of water) and gently boil the 

 mixture for twenty to thirty minutes. To minimize the loss of 

 water by evaporation the mouth of the flask should be covered 

 with a small watch-glass during the boiling process. Cool the 

 flask for two to three minutes in running water, and dilute the 

 contents to about 150 c.c. by means of cold water. Add 10 c.c. 

 of a 5 per cent solution of barium chloride slowly, drop by drop, to 

 the cold solution. The contents of the flask should not be stirred 

 or shaken during the addition of the barium chloride. Allow the 

 mixture to stand at least one hour, then shake up the solution and 

 filter it through a weighed Gooch crucible. 



Wash the precipitate of BaSCX with about 250 c.c. of cold 

 water, dry it in an air-bath or over a very low flame, then ignite, 

 cool, and weigh. 



Calculation. Subtract the weight of the Gooch crucible 

 from the weight of the crucible and the BaSCU precipitate to 

 obtain the weight of the precipitate. The weight of SOs or S in 

 the volume of urine taken may be determined by means of the 

 following proportion: 



Mol. Wt. Wt. of Mol. Wt. 

 BaS0 4 : BaSO 4 :: SO 3 : X (wt. of S0 3 in grams). 



Representing the weight of the BaSCU precipitate by y and sub- 

 stituting the proper molecular weights, we have the following 

 proportion: 



233.43 : y :: 80.06 : x (wt. of SOs in grams in the quantity 

 of urine used). 



Calculate the quantity of SOs in the twenty-four-hour speci- 

 men of urine. 



'Folin: Jour. Biol. Chem., 1905, 1, 131. 



