Chemical Apparatus. Ill 



terials in alternate layers stratum super stratum. 

 It is thus copper is converted into brass, viz. by 

 alternate layers of copper and lapis calaminaris 

 mixed with other substances : the vapours from 

 this last tinge the copper yellow. The vessels 

 for this process are chiefly crucibles. 



III. VESSELS for SOLUTION. Those of a co- 

 nical form are often very convenient, as they bear 

 sudden alterations of heat, and prevent the easy 

 escape of vapour. To this class may be referred 

 the pelican and Papiris digester. 



Solution is often partial, in which case it is 

 necessary to purity it by fdtr tion. The com- 

 mon means are through a spongy kind of paper, 

 such* as the common blotting-paper, and to se- 

 parate still farther powdery matter from fluids, 

 chalk-stone. 



Among chemical instruments may be reckon- 

 ed the iron rod, or knife for cutting glass. By 

 applying this iron red-hot we may lead a crack 

 in a glass in any direction, moving the iron a 

 little before the crack, which follows the iron. If 

 there is not a crack in the vessel, the iron must 

 be applied red-hot to the part we want to sepa- 

 rate, till the glass is well heated, and then apply 

 a file dipped in cold water to the part, and it will 

 immediately crack. 



The means of producing heat are seven, viz. 

 1. Animal Heat; 2. Friction or Percussion; 

 3. Electricity; 4. Mixture of Bodies; 5. Fer- 

 mentation ; 6. Rays of the Sun ; 7. Fuel. 



