Berzelius on the Use of the Blow-pipe. 33 1 



latter case we must employ borax and tin. If copper and iron 

 be found together, the same operation reduces each separately 

 into distinct particles, which may be known by their respective 

 colours, and separated by the magnet." 



The methods of examining the sulphurets, arseniurets, and 

 alloys, and the characteristic effects of acids, as component 

 parts of salts, are given with equal perspicuity and detail, and 

 the mode discovered by the author of detecting phosphoric acid, 

 by means of boracic acid and iron, is ingenious and useful. 



The last division is devoted to the pyrognostic characters of 

 minerals and urinary calculi, and constitutes the largest por- 

 tion of the work. In order to shew our readers the way in which 

 this important part of the subject is treated, we subjoin an in- 

 stance, taken at random, with which we shall conclude our ex- 

 tracts. 



" Chondrodite, from Pargas, Iker and America. The Bru- 

 cite of the Americans*. Alone, in the matrass, blackens by 

 heat, but gives no appreciable quantity of water ; the black co- 

 lour disappears by roasting in the open air. 



" On charcoal it is infusible. The most ferruginous chondro- 

 dite becomes opaque and brown on the points that are most 

 strongly heated. The variety containing less iron, that from 

 Iker, for instance, becomes milky Avhite, by the effect of 

 heat. 



" With borax fuses slowly, but completely, into a transparent 

 glass, slightly tinged by iron. If the glass be saturated with 

 the chondrodite, it loses its transparency by flaming; it does 

 not, however, become milky white, but semi-translucid, and 

 crystalline. 



" With salt of phosphorus decomposes pretty easily, and 

 leaves a semi-transparent siliceous residuum ; the glass is clear 

 and colourless, bat becomes opaline on cooling. A small quan- 

 tity of soda transforms it into a difficultly fusible grey scoria; 

 with a larger quantity it intumesces and becomes infusible. 



" With solution of cobalt, in a strong heat, it gives a pale red 

 colour, not pleasing to the eye. Chondrodite from Pargas 

 gives a brown grey, the action of the iron preventing that of the 

 oxide of cobalt on the magnesia." 



The portion of this work devoted to the examination of 

 urinary calculi, though brief, will be found of great utility and 

 importance, especially to medical men, to whose attention we 

 earnestly recommend it, as " simple and infallible, and requir- 

 ing no more chemical knowledge than every physician ought to 

 possess." 



* " Silicate of Magnesia. — Almost all the magiiesian silicates cotitain a 

 combustible substance, which becomes charred when heated in close ves- 

 sels. If the mineral be then heated in the open air, the charcoal burns 

 away, and the black colour disappears. Steatite is m remarkable iu- 

 itance." B. 



