292 On a new Method for the Determination of Urea. 



has two tubes, b and c, opening into it. Fig. 2. 



The tube b, 3 inches long and { diameter, 



is closed at its outer extremity ; and the 



tube c, 4 inches long and £ diameter, is 



open. The cup has three wire feet attached 



to it for supports. A glass funnel of such 



a size as to fit the cup in the way shown \A 



in the figure, is fixed therein water-tight & 



by means of a cork at d. Water is now d>\ 



poured through the tube c into the cup. <Z& / ^— ' \ 



It fills the tube b, and is allowed to reach 



the level, aa. A spirit-lamp is applied at b \ when boiling takes 



place, the waste steam escapes through c, and the funnel is thus 



kept at 212° F. 



On a filter in this funnel the contents of the two Woulfe's 

 bottles are poured, and the mouth of the funnel loosely closed 

 by a glass plate. The steam arising from the filter as it warms 

 excludes the air for the most part ; the advantage of this being, 

 that it prevents the absorption of carbonic acid from the air. 



The filtrate runs off quickly. The Woulfe's bottles are then 

 carefully rinsed out with boiled water; this is put on the filter, 

 and when it has gone through the carbonate of baryta, is 

 thoroughly washed with water to which some ammonia has been 

 added. When the washing is completed, the drop of water at 

 the tip of the funnel is removed, and the glass plate taken from its 

 mouth. The warm air now rises through the neck of the funnel, 

 and the precipitate rapidly dries. By this manipulation the funnel 

 serves the double purpose of a hot filter and a drying chamber. 



The drying is continued until the carbonate has detached itself 

 in flakes from the filter. The carbonate is then transferred to a 

 platinum crucible, and the filter burnt in a loop of platinum foil, 

 the incineration taking place without any difficulty. The weight 

 is then determined, deducting the filter-ash. 



A correction is then made, depending on the quantity of air 

 which has been run through by the aspirator, and which intro- 

 duced some carbonic acid. I have commonly employed about 

 1000 cubic centimetres, and assumed the quantity of carbonic 

 acid at j^^dth of that volume. This gives the weight of car- 

 bonate of baryta which has arisen from the urea. Then, 



As 198 : 60 : : weight of carbonate of baryta obtained : weight 

 of urea. 



It takes about two hours to make one determination in this way. 

 If solutions containing known weights of urea dried at 212° F. 

 are employed for testing the value of this process, the results 

 will be found very accurate. 



University, New York, 

 September 1, 1853. 



