WRITINGS OF JAMES SMITHSON. 51 



partly to its small quantity, which occasioned it to be spread 

 very thin on the watch-glass, and partly to its containing a 

 considerable excess of alkali, for it differed also from the 

 Palermo ulmin by becoming soft in the air, and its solution 

 strongly restored the blue colour of reddened turnsol paper. 



Nitric acid, added to a filtered solution of this ulmin, im- 

 mediately caused a precipitate in it, and the filtered solu- 

 tion, on evaporation, afforded numerous crystals of nitrate 

 of potash. 



This English ulmin made a considerable effervescence 

 "with acetous acid, which the Palermo ulmin had not been 

 observed to do. This acetous solution, in which the acid 

 was in excess, was exhaled dry, and repeatedly washed with 

 spirit of wine. No part of the brown matter dissolved. 

 "Water dissolved this brown residuum readily and entirely. 

 This solution did not sensibly restore the blue colour of 

 reddened turnsol paper. Exhaled to a dry state, the mat- 

 ter left did not separate from the watch-glass quite as freely 

 as Palermo ulmin, which had been treated with acetous 

 acid ; but it seemed no longer to grow moist in the air. 

 Redissolved in water, and nitric acid added, the mixture 

 became thick from a copious precipitate. 



The spirit of wine contained a quantity of acetate of 

 potash. 



The excess of alkali, in this English ulmin, may be owing 

 to the tree from which it was collected having been affected 

 with the disease, which produces the alkaline ulcer to which 

 the elm is subject. 



Sap of the Elm Tree. 



Thinking that the production of ulmin by the plant 

 might not be the consequence of disease, and that it might 

 exist in the healthy sap, a bit of elm twig, gathered in the 

 beginning of last July, was cut into thin slices and boiled 

 in water. It afforded a brown solution, like a solution of 

 ulmin. Exhaled to dryness, this solution left a dark brown 



