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BAIRD &TATLOCK (LONDON) LTD. 



ment the bottle is put into cold water, ami the gas tube let down into the cylinder lor a tew moments and then 

 raised until the water inside and out is on the same level, and the amount of gas collected is read off. The tube 

 is so graduated that each division represents one-tenth of i per cent, of urea. The hypobromite solution is 

 prepared by dissolving 100 grammes of caustic soda in 250 cubic centimetres of water and adding 25 cubic 

 centimetres of bromine. In order to render the preparation of the hypobromite easy to those who have no 

 laboratory, and to avoid the annoyance of the vapour of bromine, the following method has been devised by Dr. 

 Dupre : The caustic soda is supplied in bottles containing too grammes, and the bromine in hermetically sealed 

 tubes of 2.2 cubic centimetres. The additional apparatus required are first, a stoppered bottle for the prepara- 

 tion of the soda solution, marked at 250 and 500 cubic centimetres ; second, a stoppered cylinder, marked at 

 23 and 46 cubic centimetres, for the preparation of the hypobromite. Fill the stoppered bottle with water to 

 250 cubic centimetres and add 100 grammes caustic soda. Supposing hypobromite required for only one 

 experiment, pour into the graduated cylinder 23 cubic centimetres of the above soda solution, drop in gently 

 one of the 2.2 cubic centimetres of bromine, and having replaced the stopper, break the bromine tube by means 

 of a smart up and down shake ; in a few moments the bromine is dissolved and the hypobromite solution ready 

 for use, no trace of bromine vapour having escaped into the room. 



(See Journal o/ the Chemical Society, Vol. I., 1877, p. 5J4-) 



768 Urea Apparatus, Gerranl's 



768 



DIRECTIONS FOR USE. 



each 



Pour into the tube 5 cubic centimetres of the urine to be examined, and in the bottle (A) 25 cubic centimetres 

 or 6 fluid drachms of sodium hypobromite solution. Place the tube carefully inside the bottle, as shown in the 

 illustration, avoiding spilling any of the contents. Fill the glass tubes (B) (c) with water, so that the level 

 reaches the zero line, taking care that when this is done the tube (c) contains only a little water by being placed 

 high it having to receive what is displaced from (B) by the nitrogen evolved. Now connect the indiarubber 

 tubing to the bottle, and noting lastly that the water is exactly at zero, upset the contents of the tube into the 

 hypobromite solution. Nitrogen is evolved, and depresses the water in (B). When this ceases, lower (c) until 

 the level of the water in both tubes is equal. To be exact, dip (A) into cold water to cool the gas before taking 

 a reading, and note the results, which shows percentage of urea. 



The solution of hypobromite of soda is made by dissolving loo grammes of caustic soda in 250 cubic centi- 

 metres of water, then adding 22 cubic centimetres of bromine. 



To avoid the danger of the bromine vapour, the bromine is sold in hermetically sealed glass tubes, containing 

 2.2 cubic centimetres ; one of these placed in the large bottle with 25 cubic centimetres of the solution, gives, 

 when broken by being dropped on the end, the exact quantity of hypobromite for one estimation of urea, and all 

 bad odour is avoided. 



10 



-CROSS STREET HATTCTNT GARDEN, E- C 



