26 



On Ulmin. 



find possessed exactly the characters described by Klaproth. It 

 produced no effect upon litmus paper, either in its usual blue 

 state, ©r when reddened by vinegar. Hence the carbonate of 

 potash, which the ulmin contained, must have been in a state of 

 combination. 



3. No effect was produced on the solution by isinglass dis- 

 solved in water, by tincture of nutgalls, or by prussiate of 

 potash. 



4i Green sulphate of iron occasioned a very copious muddy 

 brown precipitate. 



5. Muriate of tin occasioned a copious light brown precipi- 

 tate. The same eifect was produced by nitrate of mercury, and 

 superacetate of lead. 



6. Nitrate of silver, caustic potash, and carbonate of potash, 

 occasion no precipitate. 



7. No precipitate was produced by alcohol, how much soever 

 the solution of ulmin was concentrated. In this respect, my 

 experiments differ from those of Klaproth. It is possible, that 

 •if I had employed a stronger alcohol than any I was possessed of 

 when these experiments were made, my result might have cor^ 

 •responded with that of Klaproth. 1 had not the means of 

 -determining its specific gravity. But, as it was procured from 

 an apothecary's shop in London, it vv'as probably not less than 

 -0'837. 



8. Nitric acid dropped into the aqueous solution of ulmin occa- 

 sions a reddish brown precipitate. The Hquid being cautiously 

 evaporated to dryness, a reddish matter remains, which is soluble 

 in alcohol, and has a bitter taste. When heated to a tempera- 

 ture between 300° and 400° Fahrenheit, it takes fire even in a 

 close vessel, and burns instantaneously like gunpowder, pro- 

 ducing a quantity of gaseous fluid, and leaving a black spongy 

 charcoal behind. This is owing to the nitrate of potash formed by 

 means of the potash contained in the vegetable matter. For 

 when the precipitate is separated by the filter, washed, and dried, 

 it loses the property of ex])ioding. When the liquid is gradually 

 evaporated to dryness, prismatic crystals of nitrate of potash 

 shoot at the bottom of the vessel. 



Sulphuric acid occasions ^ very copious yellowish brown 

 precipitate when dropped into the aqueous solution of ulmin. 

 Muriatic acid produces the same effect. When this precipitate 

 is well washed and dried, it is a buff-coloured powder, nearly 

 insipid, and not sensibly soluble either in water or alcohol. 



From these properties it is obvious tliat the characters ascribed 

 to ulmin by Klaproth do not apply to the substance which I 

 examined. Ulmin might be compared to extractive ; but its in- 

 solubility in alcohol seems to make it necessary to constitute it a 

 Eew genus of vegetable mattero 



