Chemical Science. 177 



the same number of concussions produces the same sound as 

 in the air. In consequence of this property of being sonorous 

 in thewater, the instrument has been called the Siren. — An- 

 'lales de Ckimip, \n. p. 167. 



II. Chemical Science, 

 § Chemistry. 



1. Separation of Magnesia arid Lime. — The separation of 

 these two earths has, at diflferent times, gained a good deal 

 of attention, both from the frequency with which they occur 

 together, and the difficulty with which they are accurately se- 

 parated. M. Longchamp has, in the Annates de Chimie, added 

 a long paper to those already published, on this subject, the 

 most important part of which is in substance as follows :— 



Oxalate of ammonia is objected to, because a portion of oxa- 

 late of magnesia is precipitated at the same time with the oxa- 

 late of lime. 



Subcarbonate of ammonia is considered as the best means 

 of separating the two earths, but care must be taken to filter 

 the solution from the precipitate which falls on its addition 

 to mixed salts of lime and magnesia, shortly after it is added ; 

 otherwise, if it stand twelve or eighteen hours, subcarbonate 

 of magnesia falls with the carbonate of lime; 100 grammes of 

 pure muriate of lime, gave, with subcarbonate of ammonia, 

 1.5475 grammes. 100 grammes of the same solution, previously 

 mixed with much muriate of magnesia, so that the latter earth 

 was in largest quantity, gave a precipitate of 1,5585 grammes 

 of carbonate of lime. 



Alkaline subcarbonates dissolve the subcarbonates of mag- 

 nesia. Well washed moist subcarbonate of magnesia was 

 agitated, and left in contact with solution of subcarbonate of 

 potash, or soda, for twenty-four hours ; then being filtered, the 

 clear liquor deposited subcarbonate of magnesia on being 

 heated, but still retained some in solution, as was shewn by add- 

 ing caustic potash. A cold solution also retains more of the 

 magnesia than a hot one; 100 parts of sulphate of magnesia. 



Vol. IX. N 



