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Notes on the Magnesite. 



Note on the Magncsite. — By the Editor. 

 (See page 24. ) 



Mr. Chamier, Chief Secretary to Government, has obligingly favour- 

 ed us with a perusal of Dr. Macleod's Report to Government, referred 

 to by Dr. Benza, but it alludes only to the properties of the Magnesite 

 as a cement, and gives no account of its chemical analysis, for which a 

 reference is made to that given by Mr. Henry, who first analysed the 

 Indian mineral. 



We subjoin an extract from the most modern work on Chemistry, 

 together with the account of Mr. James Prinsep's investigations on 

 this subject, which will inform our readers of every particular neces- 

 sary to be known. 



" Carbonate of Magnesia. — It is met with occasionally in small 

 acicular cryst als, and in a pulverulent earthy state, but more commonly 

 as a compact mineral of an earthy fracture called magnesite. A speci- 

 men of magnesite from the East Indies, where I am informed it is 

 abundant, has been analysed by Dr. Henry, who found it to be nearly 

 pure anhydrous carbonate of magnesia : it is of a snow-white colour, 

 of density 2*56, and so hard that it strikes fire with steel. (An. of Phil, 

 xm. 252). It is obtained in minute transparent hexagonal prisms 

 with 3 eq. of water, when a solution of bicarbonate of magnesia eva- 

 porates spontaneously in an open vessel. The crystals lose their 

 water and become opaque by a very gentle heat, and even in a djy air 

 at 60°. By cold water they are decomposed, yielding a soluble bicar- 

 bonate and an insoluble white compound of hydrate and carbonate of 

 magnesia; and hot water produces the same change with disengage- 

 ment of carbonic acid, without dissolving any magnesia. (Berzelius.)"* 



Analysis of Native Carbonate of Magnesia from South India. 

 By James Prinsep, Esq. 



" In my analysis of the Nerbudda dolomite, published in the Glean- 

 ings in Science, vol. L p. 267, I expressed a desire to obtain some of 

 this mineral, stated by Dr. Thompson to form " whole rocks in Hin- 

 dustan, and to contain much less carbonic acid than it ought," though 

 he was curious to know whether the interior portions of the mountain 

 might not have their full proportion." 



" My wish has at length been gratified by Dr. Malcolmson, Secre- 

 tary Medical Board at Madras, among whose specimens, recently pre- 

 sented to the Society, are several lumps of this curious mineral. 

 Dr. M. writes : " The native carbonate of Magnesia from Salem has 

 again attracted attention. I at first supposed it to be a Magnesite, from 



Turner's Elements of Chemistry, p. 738. 



