448 



resinous matter no longer soluble in water, but now rendered soluble 

 in alcohol, by a supposed union with oxygen derived from these acids. 



Mr. Smithson being in possession of ulmin, sent to him from Pa- 

 lermo by the same person who had furnished M. Klaproth with the 

 subject of his researches, has made various experiments, which lead 

 to a different opinion of its nature from that which has been enter- 

 tained. 



When ulmin is dissolved in water, a dilute solution is yellow ; but 

 when concentrated, it is of a dark red, like blood. This solution 

 slowly and feebly restores the colour of turnsol, after it has been red- 

 dened by an acid. Most acids occasion a copious precipitate from 

 this solution of the matter which has been considered as resin. The 

 solution, however, still retains a slight yellow colour, from a small 

 quantity of this matter which remains dissolved. By evaporation of 

 the solution a salt is obtained, consisting of potash combined with 

 the acid employed in the experiment ; and the quantity of potash, by 

 various trials, amounted to about one fifth part of the weight of the 

 ulmin. 



The precipitate, when dried, is very glossy, and has a resinous ap- 

 pearance. In minute fragments it is found to be transparent, and of 

 a deep garnet colour. It burns with flame, and is reduced to a 

 white ash. 



Alcohol does dissolve it, but very sparingly. 



Water also dissolves a small quantity, and the solution seems to 

 redden turnsol. Neither ammonia nor carbonate of soda promote its 

 solution in water ; but a small quantity of potash dissolves it imme- 

 diately, and abundantly, and appears to regenerate ulmin, with all 

 its original properties. 



Hence Mr. Smithson infers, that ulmin is not a simple vegetable 

 principle of anomalous qualities, but a combination of potash, with 

 a matter more nearly allied to the extractives than to the resins. 



The author has also investigated the properties of a substance ob- 

 tained from the elm-tree in this country, which differed from that of 

 Palermo in containing a redundant quantity of potash in the state of 

 carbonate. He also made experiments on the sap of the elm-tree, 

 from which, however, he did not succeed in obtaining ulmin. 



On a Method of Freezing at a distance. By William Hyde Wollaston, 

 M.D. Sec. R.S. Read December 17, 1812. {Phil. Trans. 1813, 

 p. 71.] 



The method here described by the author, is performed by means 

 of an instrument, to which he gives the name of Cryophorus, ex- 

 pressing its office of frost-bearer. It consists of a tube, which may 

 be two or three feet long, or even more, terminated by a ball at each 

 end. One of these balls contains a small quantity of water to be 

 frozen, and the rest of the instrument is as complete a vacuum as can 

 be obtained. 



In making this instrument, one of the balls terminates in a capillary 



