138 THE SECRETIONS : 



weight. The following salts remain : chloride of potassium, 

 chloride of sodium, and carbonate of soda ; the latter correspond- 

 ing with the lactates. 



6. Determination of the alcohol-extract, the lact ate of ammonia, 

 and chloride of ammonium. 



These are the most difficult constituents to determine. I 

 proceed in the following manner : the alcoholic fluid (A) ob- 

 tained from the precipitation of the spirit- extract, is evaporated 

 on the water-bath to the consistence of a thick syrup, and after 

 being thoroughly dried over sulphuric acid in a receiver, is 

 weighed. The residue is dissolved in a little water, and free 

 baryta gradually added, a gentle warmth being kept up as long 

 as it continues to dissolve, and as long as ammonia is perceptibly 

 evolved. This point being attained, the mixture is evaporated 

 to the consistence of an extract, and moistened with a little alco- 

 hol of 0*83; a large quantity of anhydrous alcohol is then added, 

 and the whole allowed to clear itself. There remain undissolved, 

 chloride of barium, a compound of baryta with extractive matter, 

 and the greater part of the free baryta, which has probably been 

 added in excess. Dissolved in the alcohol are urea, lactate of 

 baryta, and a small quantity of free baryta. The undissolved 

 portion is burnt in a platinum crucible, the residue incinerated, 

 and the ash digested in water. The solution must be filtered, 

 slightly acidulated with nitric acid, and the chlorine then preci- 

 pitated by nitrate of silver. The chloride of ammonium can 

 be calculated from it. 



The alcoholic solution must be evaporated, the residue dis- 

 solved in water, the solution filtered, and a current of carbonic 

 acid passed through it, until the free baryta is precipitated : it 

 must then be again filtered, acidulated with nitric acid, and the 

 baryta of the lactate of baryta precipitated by sulphuric acid. 

 The lactate of baryta must be estimated from the residual 

 sulphate. 



By subtracting from the solid residue of the alcohol-extract 

 the weight of the urea, of the free lactic acid, of the lactate of 

 ammonia, and chloride of ammonium, we obtain the quantity of 

 the alcohol-extract. 



