On terpentine. 33 



those of any other country. The demand for such materials 

 ;among us is already considerable, and will rapidly increase with 

 Avealth and taste. May we not hope to see the new cathedrals 

 which are soon to adorn our city, decorated with Canadian mar- 

 bles ? 



There is another economical application of serpentine which 

 has now become of some importance. That of Newburyport, in 

 Massachusetts, is ground to powder, and by a peculiar process 

 impregnated with different vegetable and mineral colors, forming 

 thus cheap and valuable paints, which are extensively used in the 

 •United States. We are informed, that the serpentine is partially 

 decomposed by sulphuric acid, and that the colours seem to unite 

 with the liberated silica, which plays a part analagous to that of 

 -alumina and oxyd of tin in the lakes. 



In France, serpentine is also turned to account as a source of 

 mao-nesia and maffnesian salts. We have already seen that sul- 

 phuric acid decomposes serpentine with the formation of sulphate 

 of magnesia. As a preliminary operation, the mineral is calcined 

 at a strong red heat for forty-eight hours in a reverberatory fur- 

 nace, which holds about two and a half tons. This calcination 

 has for its object to render the iron almost insoluble. The cal- 

 cined serpentine is then ground to powder, and mixed with a 

 quantity of sulphuric acid, not quite sufficient to combine with all 

 the magnesia. The mass becomes hot, and is converted into a 

 paste of sulphate of magnesia, which is leached in large vats, as 

 in the preparation of potash ; the silica and oxj'd of iron remain 

 behind. A little milk of lime is added to the liquid to get rid of 

 2l small portion of iron and some other impurities in the solution, 

 which, when then boiled down and crystallized, yields pure 

 sulphate of magnesia — the Emom salt of the apothecaries. 

 There is an establishment of this kind at Ramiremont, in the 

 Vosges, which has been in operation for nearly twenty years, and 

 produces annually 80,000 or 90,000 pounds of sulphate of mag- 

 nesia, which is sold at about eighteen shillings the hundred pounds, 

 which is said to be only one-third the price of that imported. 



Serpentine contains on an average 40 per cent, of magnesia, 

 ■and crystallized sulphate of magnesia consists of 16.25, sulphuric 

 acid 32.50, water 51.25, = 100.00, or one equivalent of magnesia 

 20, one of sulphuric acid 40, and seven of water 63, = 126. 

 It will be seen then, that 100 pounds of serpentine, contain- 

 ing 40 of magnesia will require 80 pounds of dry sulphuric acid, 



