Analyfis of Gted.—Artijicial Roch Crjjlal. 217 



A 'Keiv liLethod f'ji- feparat'uig Manganefe and Iron., and delermimng their Pi-oportions- 



THE uncertainty of the methods propofed by chemifts to afcertain and determine the 

 quantities of manganefe contained in different kinds of iron and fteel, induced me to feek 

 another which combines fimpliclty and accuracy. I think 1 have obtained, in ilils refpeft, 

 all the fuccefs which can be defired in a matter of fuch importance. 



For this purpofe, a known quantity of iron crude or malleable, or of (lee!, fufpeiflcd to 

 contain manganefe, is tu be diflblved in fulphuric acid, diluted with four or five parts of 

 water. The folution is to be precipitated with the cauflic alkali ; and the precipitate, after 

 waftiing, and drying in the air, is to be calcined under the muffle of the aflVy :r's furnace. 

 When the calcination is as much advanced as it can be Ijy this method, the metallic oxide is 

 to be weighed, and diflblved in muriatic acid ; and after having evaporated the cxcefs of acid, 

 a folution of carbonate of pot-alh, well faturated with carbonic acid, is to bi: poured into 

 the fluid diluted with water, until no more precipitate is afforded. The filtered liquor is 

 then to be boiled; and if it contains the oxide of manganefe, this metal will fall down in thi; 

 form of a white powder, which is a true carbonate of manganefe. 



This procefs is founded on the confideration that the carbonate of pot-afti, well faturated 

 with carbonic acid, does not precipitate the falts of manganefe, becaufe the quantity of car- 

 bonic acid contained in the pot-afli neceflary to the faturation of the acid, united to the 

 oxide of manganefe, is fulEciently great to hold the latter fubflance in folution; whereas 

 the ferruginous falts, when their bafis is highly oxided, are entirely precipitated by the fame 

 re-agents. 



On this fubjefl: I have made many experiments, fynthetical and analytical, upon very 

 fmall quantities of iron and of manganefe, which have left me no doubt with regard to the 

 accuracy of the method. But the manganefe exifts in iron in the metallic (late ; and in 

 the prefent experiment it is obtained in combination with oxigene and carbonic acid. It is 

 neceffary, therefore, to divide the mafs, after drying it in the air, by 2,5. Thus, if lOO 

 parts of carbonate of manganefe be obtained, the metallic part will be 100 divided by 2,5, 

 that is to fay, 40. 



I have not yet had occafion to apply this method to a very great number of fpecimens of 

 Ileel or iron; thofe which I have hitherto examined have exhibited no traces of manganefe. 

 Whence I am llrongly inclined to think that Bergman, who found this fubftance in every 

 kind of iron and (led, mud frequently have midaken iron for manganefe, particularly in the 

 iiiflance where he affirms that he obtained 30 per cent. 

 [ To he conliiwnl. ] 



v. 



Defcriptlon of an Arlifdal Rock Cryfn! produced in the Humid JVay. By M. TrOMMR3-> 

 VOasj-, Profi-Jjor of Chewijlry at the Univerftiy of Erfurt *. 



T is well known that fdcx, either pure, or mixed with heterogeneous fubftances, and cry- 

 ftallized in beautiful tranfparcnt columns, conditutes rock crydal. The curious enquirer, 



" Journal Jcr Pharmacic fur Ante Apothtkcr und Chcmiftcii, x Bjnd. i St. pag. 76. 



Vol. I. — August 1797. F f who 



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