70 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE. 



Fig. 508. 



Blow-Pipe. (Fig. 508, as above.) This is an instrument 

 by which a small jet of air is directed laterally into the 

 flame of a lamp or candle, so as to divert it in a long slender 

 cone upon a piece of charcoal or other substance so placed 

 as to receive it. When a flame is thus urged by the blow- 

 pipe, the extreme heat is just at the tip of the outer white 

 flame, where the combustion is most perfect, and where 

 substances are rapidly burned or oxidized ; whilst the inte- 

 rior blue flame, in consequence of its excess of combustible 

 matter, abstracts oxygen from, or reduces substances. So 

 that several metals, when thus heated before the blow-pipe, 

 are alternately oxidized or de-oxidized by being placed in 

 the outer and inner flame. The blow-pipe is of important 

 service to the chemist, in enabling him to ascertain easily 

 and quickly, the effects of intense heat upon a variety of 

 substances ; and he frequently has recourse to it in order to 

 distinguish metallic and earthy minerals from each other, 

 and to ascertain in a general way, the nature of their com- 

 ponent parts. Price, 3 Sets, and 50cts. 



Blow pipes, with reservoirs for condensing the moisture 

 of the breath. Price, 63cts. and $1.50. 



Fig. 509. 



Crucibles. (Fig. 509.) The cru- 



Qcible is a vessel usually made of well 

 hardened earthen or stone ware, in 

 constant use in the chemical labora- 

 tory for performing fusions of metals 

 and other substances. 



Price, 6 cts. to 38 cts. per nest. 



