CHEMICAL SCIENCE. 253 



Acetometer. Carbonate of soda. Carbonate of baryta. 



6-3 6-5 6-2 



9-1 9-2 9-0 



For testing with carbonate of soda, a solution was prepared, containing 104 

 grm. in a litre. Five cub. cent, of this solution indicated in 50 grm. of vine- 

 gar one per cent, of anhydrous acetic acid. The point of saturation was 

 determined by means of pale-blue litmus paper. 



For tasting with carbonate of baryta, a weighed quantity was digested 

 with a weighed quantity of vinegar, with the aid of heat, until the liquid 

 acquired an alkaline reaction. The undissolved carbonate of baryta was 

 collected upon a filter, washed, dried, ignited, and weighed. 



In order to remove the objection that the digestion with carbonate of 

 baryta had not been continued long enough, the following experiment was 

 made: A solution was prepared, containing in 100 grm. 27 grm. of crystal- 

 lized acetate of soda. This solution contained 10 grm. or 10 per cent, of 

 acetic acid. It had an alkaline reaction upon red litmus paper. When 

 mixed with 2 cub. cent of vinegar, containing 4'5 per cent, acetic acid, it 

 became perfectly natural, and another cubic centimeter of vinegar was suffi- 

 cient to make it have a decided acid reaction upon blue litmus paper. The 

 quantity of acetic acid in 2 cub. cent, of vinegar, containing 4'5 per cent, of 

 acetic acid, is not quite O'l grm.; so that the error incurred by estimating 

 the amount of acid in vinegar, containing 10 per cent, acetic acid, by means 

 of carbonate of soda, would be only -J^ per cent, at the utmost, and is cer- 

 tainly much less, because in practice there is always a little excess of soda 

 added. 



A hot solution, containing 50 per cent, of acetate of soda, corresponding 

 to 18'7 per cent, acetic acid, was rendered neutral by 2 cub. cent, of vinegar, 

 containing 9 per cent, of acetic acid, and distinctly acid by 1 cub. cent, more 

 vinegar. 



Prof. Otto infers from these results that the estimation of the amount of 

 acid in vinegar, by means of carbonated or caustic alkalies, may be adopted 

 without the risk of any sensible error, inasmuch as the alkaline reaction of 

 the alkaline acetates do not affect the results to such an extent as need be 

 regarded in practice. 



He also remarks, that a comparison of the relation between the density of 

 ammonia solution and the amount of ammonia contained in it, as estimated 

 by him some years since, with the results obtained recently by Carius in a 

 very different manner, shows a very close correspondence. 



NEW PROCESS OF PRESERVING MILK PERFECTLY PURE IN THE 

 NATURAL STATE, WITHOUT ANY CHEMICAL AGENT. 



At the Aberdeen meeting of the British Association, the Abbe Moigno 

 stated, " that to preserve milk for an indefinite period, is an important prob- 

 lem, which in France has been solved in three different modes. M. de Yil- 

 leneuve was the first to preserve milk, solidifying it by the addition of certain 

 solid ingredients, but it was no longer, properly speaking, milk. M. de 

 Signac preserved it by evaporating the milk till it became of the consistence 

 of sirup, rendering it a solid mixture of milk and sugar; still it could not be 

 called milk. M. Maben also preserved it by excluding the air, and exposing 

 it to-an atmosphere of steam about 100 3 Cent. thus depriving it of all the 



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