49 



a in front. If the upper meniscus line of the urine is between 

 any of the 0.1 ccm. marks, the upper number should be read. 



The figures to the left of the apparatus refer to the number 

 of cc. of urine added to the mixture. 



Should the urine contain less uric acid than the apparatus 

 will in this way indicate, add the iodine solution to the mark half 

 way between ^ and J and read after each reaction the half values. 



The vessel in which the urine is to be kept, must not be 

 cleaned with soda. 



If the urine shows an acid reaction, it can be used at once, 

 but if it should be alkaline, it has to be made acid by adding 

 diluted acetic acid. Cloudiness is of no importance. 



If the urine contains a considerable sediment of sodium urate 

 it should be well shaken. 



Strong colorations of the urine do not affect the action of 

 carbon bisulphide. 



Traces of sugar and albumin do not disturb the result. 



If there is a very large percentage of albumin or traces of 

 blood or pus, these pathologic substances have to be coagulated 

 by boiling and the urine filtered. 



The apparatus is not satisfactory for determining the uric 

 acid in the urine of the horse. 



(The uricometer may be purchased of Eimer & Amend, New 



York). 



Cook's Method of Estimating Uric Acid hy the Centrifuge. 

 Place in the graduated tube 10 cc. of urine; add to this 1 gm. of 

 sodium carbonate and 1 cc. of ammonium hydrate. Sliake until 

 the sodium carbonate is dissolved; this precipitates the earthy 

 phosphates. Separate this precipitate with the centrifugal ma- 

 chine and decant the supernatant urine into another graduated 

 tube. It will be found that the earthy phosphates are readily 

 separated and adhere to the bottom of the tube; this allows the 

 clear urine to be readily poured off into another tube. To the 

 clear urine now free from phosphates add 2 cc. of ammonium 

 hydrate and 2 cc. of ammonio-silver solution (made by dissolving 

 5 gm. of silver nitrate in 100 cc. of water and adding ammonia 

 until the solution becomes clear). The addition of the silver 

 solution causes the uric acid to be precipitated as the urate of 

 silver, a translucent, shiny substance. Separate this precipitate 

 with the centrifugal machine and pour off the supernatant urine. 

 Add to the ppt. an excess of ammonium hydrate, at least 15 cc. 

 and mix thoroughly. By this last addition any of the chlorides 

 that may have been precipitated are redissolved leaving only a 

 pale urate of silver. Lastly precipitate this urate of silver until 

 the lowest reading is to be had. Each 0.1 cc. as marked on the 

 graduated tube indicates 0.001175 gram of uric acid in 10 cc. of 



