330 HOW TO SEE WITH THE MICROSCOPE. 



volume of this mixture three-fold by the addition of 

 water; fill the burette with standard solution, and 

 have in readiness a white plate or saucer, on which 

 have been placed several separate drops of the ferro- 

 cyanide. Heat the contents of the beaker over the 

 spirit-lamp, and keeping the same tolerably warm,, 

 tritate with caution, and when a drop from the beaker 

 on being placed in contact with the ferro-cyanide 

 strikes a brown color, the analysis is ended; and if the 

 standard solution is of the proper strength, the burette 

 will read at the 100 mark. Any error of standard 

 solution noticed is to be corrected and the analysis re- 

 peated with the standard solution as amended. 



Analysis of Urine for Phosphoric acid. With 

 the pipette measure two fluid drachms of the urine 

 into a beaker, and to this add one-half drachm of the 

 acetate of soda solution, also an extra drachm or so of 

 water; have ready the white plate and the ferro-cyanide 

 solution; warm the contents of the beaker over the 

 spirit-lamp, and maintaining the heat, tritate as in the 

 above test; continue the addition of the standard solu- 

 tion until the drop from the beaker when in contact 

 with a drop of the ferro-cyanide shall strike a brown 

 color, which terminates the analysis. Read the burette,, 

 the number shown divided by fifty will indicate the 

 number of grains of phosphoric acid to the fluid ounce 

 of urine. 



Analysis with the Marais Approximate Tubes. 

 The tube is to be filled to the ounce mark with filtered 

 urine, add also two drachms of the acetate of soda solu- 



