WRITINGS OF JAMES SMITHSON. 49 



magnesia ; but these can be considered only as foreign ad- 

 mixtures. 



4. To acquire an idea of the quantity of potash in ulmin, 

 4 grains of ulmin were decomposed by nitric acid. They 

 afforded 2.4 grains of resin-like matter. The nitrate of 

 potash obtained was heated to deflagration, in small quanti- 

 ties at a time, in a platina crucible to free it from resin. 

 The alkali produced was supersaturated with nitric acid, 

 dried, and slightly fused. It then weighed 1.2 grains. If 

 we admit ^ of nitrate of potash to be alkali, this will denote 

 ■^^ of potash in ulmin. 



6 grains of ulmin were decomposed by muriatic acid. 

 The resinous matter weighed 3.3 grains, and the muriate of 

 potash, after being ignited, dissolved away from the char- 

 coal, dried, and again made red hot, weighed 1.4 grains. 

 If we suppose § of muriate of potash to be alkali, this will 

 indicate jy^ of pota«h in ulmin. 



2 grains of ulmin were made red hot in a gold crucible. 

 It then weighed only 1.05 grain. The form of the flakes 

 was in no degree altered, but they had acquired the blue 

 and yellow colours of heated steel, of which they had like- 

 wise the metallic aspect and lustre, and could diflicultly, if 

 at all, have been distinguished by the eye from heated steel- 

 filings, or fragments of slender watch-springs. Water im- 

 mediately destroyed their metallic appearance. 



Muriatic acid, poured on, caused a strong effervescence, 

 and formed muriate of potash, which, freed from all char- 

 coal, and made red hot, weighed 0.6 grain, corresponding 

 to 3^ of potash in ulmin. 



These experiments assign about ^ for the quantity of 

 potash in ulmin, but as it is impossible to operate, on so 

 small a scale, on such substances without loss, it is proba- 

 ble that it even exceeds this proportion. 



5. The substance separated from ulmin by acids has the 

 following qualities : 



It is very gloss}', and has a resinous appearance. 

 '4 



