86 WRITINGS OF JAMES SMITUSON. 



paper. Possibly a small remainder of muriatic or sulphurip 

 acid among it is required for this effect. 



9. JSitric Acid. — Nitrate of ammonia produces no defla- 

 gration when filtering paper, wetted with a solution of it and 

 dried, is burned ; the salt volatilizing before ignition, most, 

 or all, the other nitrates deflagrate. 



If metallic copper is put into the solution of a nitrate, 

 sulphuric acid added, and heat applied, the copper dissolves 

 with effervescence. 



10. Carbonic Acid. — It is to be discovered in the mineral 

 itself. The application of heat is, in some cases, required 

 to render the effervescence sensible. It has been sometimes 

 overlooked in bodies from want of attention to this circum- 

 stance. 



11. Silica. — A simple and suflScient test of it is the form- 

 ation of a jelly, when its combination with soda is put into 

 an acid. 



It has evidently not been intended to enumerate all the 

 means by which the presence of each acid in the soda bead 

 could be perceived or established. Little has been said be- 

 yond what appeared required and suflicient. 



Mention has been made above of small plates of clay. 



They are formed by extending a white refractory clay by 

 blows with the hammer, between the fold of a piece of 

 paper, like gold between skins. The clay and pap6r, are 

 then cut together with scissars into pieces about 4-lOths of 

 an inch long, and 2^-10th3 of an inch wide, and hardened 

 in the fire in a tobacco-pipe. 



They are very useful additions to the blowpipe apparatus. 

 They admit the use of a new test, oxide of lead. They 

 show to great advantage the colours of matters melted with 

 borax, &c. Quantities of matter too minute to be tried on 

 the coal, or on the platina foil, or wire, may be examined 

 • on them alone, or with fluxes. Copper may be instantly 



