328 HOW TO SEE WITH THE MICROSCOPE. 



read at the one hundredth mark ; if too strong- or too 

 weak, add silver or water as the case may demand, and 

 repeat the test. The indications of the burette furnish 

 a ready guide as to the amout of correction necessary, 

 hence the second test ought to be sufficient. 



Analysis of Urine for Chloride of Sodium. Filter 

 say one-half ounce of the urine, and with the measur- 

 ing pipette introduce one fluid drachm of the filtered 

 urine into a wine-glass, and add three volumes of dis- 

 tilled water, and also two or three dr^ps of the satu- 

 rated potash solution. Now with a bit of litmus paper 

 test the reaction of the mixture ; it should be rendered 

 faintly alkaline by adding Carbonate of soda, or dilute 

 nitric acid as may be found necessary. Fill the burette 

 and tritate according to the directions given above, 

 until the permanent precipitate makes its appearance. 

 Now read the burette, divide this number by twenty- 

 five which will give you the number of grains of 

 chloride of sodium per fluid ounce of urine. 



Should the specimen of urine be very high colored 

 it may be somewhat difficult to detect the first appear- 

 ance of the permanent precipitate, hence the accuracy 

 of the analysis will be impaired. In such cases, there- 

 fore, it is better first to decolorize the urine; this is 

 tolerably well accomplished by adding a drop or two of 

 a solution of permanganate of potash, and with the 

 spirit-lamp bring the mixture nearly to the boiling 

 point. A brown precipitate will be observed which is 

 to be removed by filtration, and the filtrate used for 

 the analysis according to the preceding directions. 



