Rapid Estimation of Urea. 



149 



inches to expel 6 J drachms of water, the volume of liquid in the 

 bottle A being three drachms, and the hypobromite added ten 

 drachms. 



It may be mentioned that measures of capacity need not be 

 employed in the determinations of urea, as the water expelled 

 may be received in any suitable vessel which has been pre- 

 viously weighed. At the end of the experiment the vessel and 

 expelled water are weighed. When the estimation was made, 

 under the conditions above named, one grain of urea was found 

 to expel, as a mean, 365 grains of water by weight. This 

 number is easily remembered, as it happens to be identical with 

 the number of days in a year. 



Effect of the Degree of Dilution upon the Determination of 

 Urea. — An apparently trifling observation led me to examine 

 the effect of dilution upon the yield of nitrogen obtainable from 

 a constant weight of urea ; and the results arrived at are stated 

 in the Table given below. 



The quantity of pure dry urea operated with in each of the 

 following experiments was 2*222 grains ; and the same volume 

 (i. e. ten fluid-drachms) of a single sample of freshly prepared 

 sodic hypobromite was added in each case. The experiments 

 were completed within three and a half hours ; and care was 

 taken to avoid changes of temperature as much as possible : 

 hence, while the barometer remained steady at 30*06 inches, 

 the temperature varied within such very narrow limits (be- 

 tween 50° and 52° F.) that corrections for alterations of 

 volume were unnecessary, as extreme accuracy in the measures 

 of the water expelled was not attainable with the vessels ad- 

 visedly employed, as I desired the results to be of such a kind 

 as a medical man could easily obtain in his own study. 



Table. 



No. of 



Pure dry urea 



Volume of water 



Volume of 



experi- 



used in 



used to dissolve 



water expelled 



ment. 



experiment. 



urea in A. 



from F. 



1. 



2-222 grains. 



drachm. 



15^ drachms. 



2. 



5J 



1 



15 



3. 





2 drachms. 



14§ „ 



4. 



JJ 



2 





14| 



5. 



„ 



3 





14| u 



6. 



>> 



3 





143 „ 



7. 



>J 



4 , 





14| „ 



8. 



>> 



5 





Lost. 



9. 



» 



6 





14 + „ 



10. 



» 



7 , 





13§ „ 



11. 





8 





13* „ 



12. 



>> 



9 , 





13| + » 



13. 



>1 



10 





13| + „ 



