APPARATUS. 323 



lessly pouring the remaining contents of the burette 

 (after an analysis) into the wrong bottle. The same 

 glass rod ought not to be used in different solutions 

 without being cleansed. !Every bottle should have its 

 own stopper, and these should not become interchanged. 

 Every piece of apparatus used in an analysis should, at 

 the termination thereof, be immediately cleansed. 



The practitioner will find it convenient to make his 

 several standard solutions in quantities of 3,000 grains. 

 With the exception of the one used for the determina- 

 tion of sugar, they all have reliable keeping properties, 

 and as 3,000 grains can be made with about as little 

 trouble as 1,000, it is an economy of time to do so. 



Procure, if possible, suitable bottles for the standard 

 solutions, furnished with a "pouring lip." These are 

 so much handier in filling 1 the burette. Ours were ob- 



O 



tained from an ink manufactory, and answer the purpose 

 perfectly. 



Analysis for Urea Standard Solution. Weigh 

 thirty-eight and six-tenths grains of pure red oxide of 

 mercury and place the same in a large test tube, add a 

 little nitric acid, c. p., and apply the heat from the spirit 

 lamp. The oxide will appear to crust and little inclined 

 to dissolve. By keeping up an uniform heat, mean- 

 while stirring with a glass rod, the oxide will become 

 gradually dissolved. Should it, however, become neces- 

 sary, add a little more acid carefully, little by little, 

 maintaining the gentle heat and stirring with the rod 

 until all of the oxide shall be dissolved, the object being 

 to use the least amount of acid possible. The process 



