310 M. Nordenskiold on Zinc Ores 



But its chemical composition, besides, is different, since it 

 is an arseniate of lime and magnesia. I possessed too small a 

 quantity for determining the relative quantities of the lime and 

 magnesia to my own satisfaction, but the arsenic acid amounts 

 to 74.43 per cent. In containing magnesia, it is analogous to 

 the picropharmacolite from Riegelsdorf in Hessia, analyzed 

 by Professor Stromeyer ; but obviously differs from it, first, 

 in containing no oxide of cobalt ; and, secondly, in the pro- 

 portion of its constituents. 



Art. XIX. — On the Chemical Characters of Zinc Ores, ex- 

 amined in the manner of Berzelius, by means of the Blow- 

 Pipe. By M. Nils Nordenskiold of Abo. 



Dear Sib, 19 Charlotte Square. 



I beg to send you a copy of some memoranda of M. Nordenskiold's, relat- 

 ing to the chemical properties of some of the Zinc ores he found in my 

 Cabinet. As these minerals are not very well known, they may be useful 

 to your readers, as pointing out very simple means of discriminating sub- 

 stances which bear a strong analogy to each other. 



Yours sincerely, 

 To Dr Brewster. T. Allan- 



The mineral from Aachen contains two different substances, 

 viz. the Carbonate of Zinc, and the Siliceo-Carbonate 

 of Zinc. 



The former presents the metastatique crystal of a pale yel- 

 low colour. In a matrass it gives off easily carbonic acid, 

 without any trace of water ; the crystals preserve their form 

 after being heated, they do not fuse; and produce in a strong 

 heat an intense light of a yellowish white tint. 



With salt of phosphorus it unites with ease, turns opaque 

 in cooling, and leaves a white ring of oxide of zinc on the 

 charcoal round the globule. If the quantity of the mineral 

 be small in proportion to the salt, it will be clear even in 

 cooling, and none of the fumes of zinc can be driven from 

 the globule, even by a strong heat. 



With borax it readily unites ; the glass takes a great 

 quantity of the mineral to render it opaque in cooling. Soda 

 produces scarcely any effect upon the mineral, if exhibited in 



