COMPOUND BLOWPIPE. 227 



Effects of the compound blowpipe. 



1. Every variety of mineral matter has been melted by it, except 

 the diamond ; it is evident that this substance and charcoal are ex- 

 ceptions, merely on account of their combustibility. 



2. All combustible bodies burn in the focus, not excepting any of 

 the metals : the latter exhibit beautiful phenomena, depending on the 

 color of their oxides and of the flame : platinum, because it is too fixed 

 a substance to form vapor, burns, not with flame but with scintillation. 



3. Peculiar facilities are afforded by having two separate reser- 

 voirs for the gases. 



(.) We use the hydrogen flame alone if we wish a lower degree 

 of heat. 



most part of brass, but at its lower end terminates in a tube of platina. It communi- 

 cates by lateral apertures with the cavity of the upper ball, but is prevented by the 

 cork, from communicating with the cavity in the other ball. Hence it receives any 

 gas which may be delivered into the upper ball from the lateral pipe which enters 

 that ball, but receives none of the gas which may enter the lower ball, B." 



" Into the female screw of the latter, a perforated cylinder of brass, c, with a cor- 

 responding male screw, is fitted. The perforation in this cylinder, forms a continu- 

 ation of that in the ball, but narrows below, and ends in a small hollow cylinder of 

 platina, which forms the external orifice of the blowpipe, 0." 



" The screws, s s s s, are to keep, in the axis of the larger ball, the tube which 

 passes through it, from the cavity of the smaller ball. The intermediate nut, by 

 compressing, about the tube, the cork which surrounds it, prevents any communf- 

 cation between the cavities in the two balls. By the screw, s, in the vertex, the 

 orifice of the central tube may be adjusted to a proper distance from the external 

 orifice. Three different cylinders, and as -many central tubes, with platina orifices 

 of different calibres, were provided, so that the flame might be varied in size, agree- 

 ably to the object in view." 



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