59 



.005 X 24.3 cc. 



X 1180 = 2.86 grams P2O5. 



50 



A shorter and approximately accurate method based 

 on the above is as follows : To 10 cc. of the urine in a 

 test tube add 1 cc. of sodium acetate and 1 cc. of the 

 cochineal solution and boil. Add 5% uranium nitrate 

 solution, 1 minim at a time, boiling after each addition, 

 until the mixture turns green. Each minim of the 

 uranium solution represents 0.046 gram of PoOg in 1000 cc. 

 of urine. Multiply .046 by the number of minims re- 

 quired to produce the green color, and the product will 

 represent the amount in grams of PgOg per liter in the 

 given sample of urine. 

 Estimation of Total Sulphuric Acid. (Estimated at SO3). 

 Dissolve 30.5 grams of pure crystallized chloride of barium in. 

 some distilled M-ater and dilute to 1 liter. Each cc. of this solu- 

 tion will equal .01 gram of SO3. A dilute solution of sodium 

 or magnesium sulphate will also be required. 



Application. 50 cc. of clear urine are poured into a 

 beaker, acidified quite strongly with hydrochloric acid, 

 and heated over the flame. Let the solution boil for about 

 ten minutes, the lamp is then removed and the barium 

 chloride is allowed to flow slowly from the burette into 

 the beaker and it must continue to flow as long as the 

 precipitate is seen to increase. The precipitate is allowed 

 to subside, then more of the barium chloride is added, and 

 this process repeated, until no further precipitate is pro- 

 duced. Much time and labor will be saved by filtering a 

 feAV drops of the solution now and then, and allowing 

 these to drop into the test tube containing some of the 

 dilute sodium or magnesium sulphate. As soon as an ex- 

 cess of the barium chloride has been added, a precipitate 

 will appear in the test tube. Read off from the burette , 

 the amount of barium chloride used ; each cc. of which will 

 indicate .01 of a gram of SO3 in each cc. of urine, and 

 from this the total amount may be calculated. 



Example : Urine 2000 cc. Amount of barium chloride 

 solution 25 cc. 



