252 Dr, Henry's A nalysis of a [April, 



mined are even numbers. It is obvious that this rule cannot 

 apply to those atoms of compound bodies which contain hydro- 



fen as a constituent. Thus the weight of an atom of water is 

 •125, of an atom of muriatic acid 4*625, of an atom of ammonia 

 2*125. In the tables inserted at the end of the last edition of 

 my System of Chemistry many exceptions to this law occur. 

 The reason of this is, that though aware of the law, I did not 

 choose to alter any of the atomic weights previously determined 

 till I had satisfied myself, by unexceptionable experiments, that 

 the old numbers are erroneous. 1 have httle doubt that the 

 atoms of bismuth, tin and antimony, and aluminum, are inaccu- 

 rate, though I have not hitherto hit upon any mode of determin- 

 ing the true atomic weights of these bodies, which is quite free 

 from ambiguity. The weight of bismuth, instead of being 8*875, 

 as I have given it, is either 9, or 9*25 ; I am not quite sure at 

 present which of the two ; but as soon as I have obtained satis- 

 factory results for these, and the other simple bodies hitherto 

 remaining undetermined, I shall lay them before the public. 



Article II. 



Analysis of a Native Carbonate of Magnesia from the East 

 Indies. By William Henry, MD. FRS. &c. 



(To the Editor of the Annals of Fhilosophy,) 



Manchester^ March, 1 82 1 . 



I WAS indebted to the kindness of Dr. Babington for a speci- 

 men of this mineral. He informed me that it was brought by 

 his son from the East Indies ; but as he has given me no 

 account of its geographic situation or geognostic relations, I 

 can only describe its external characters, and state the results 

 of its chemical analysis. 



It occurs massive. Its colour is snow-white, with the excep- 

 tion of a few small dots and stripes of ochre yellow. Its fracture 

 is small conchoidal passing into uneven. It gives sparks with 

 steel, and is not easily scraped by a knife, but is not hard enough 

 to scratch fluor spar. Its fragments are sharp edged. Inter- 

 nally it has no lustre. It is very slightly translucent, and that 

 only at the edges. Its specific gravity is 2*5615. 



It dissolves in acids at ordinary temperatures with extreme 

 slowness, even when finely powdered, and whatever may be the 

 specific gravity of the acid ; but by heat its solution is quick- 

 ened, and carbonic acid is disengaged. This property is an 

 obstacle to the determination of its proportion of carbonic acid, 

 which cannot well be learned in the common way. To ascer- 



