216 



the idea of mechanic force, in practice, is always the same, and is 

 proportional to the space through which any moving force is exerted, 

 or to the square of the velocity of a body in which such force is ac- 

 cumulated. 



Me"moire sur les Quantitds imaginaires. Par M. Bue'e. Communicated 

 by William Morgan, Esq. F.R.S. Read June 20, 1805. [Phil. 

 Trans. 1806, p. 23.] 



Chemical Experiments on Guaiacum. By Mr. William Brande. Com- 

 municated by Charles Hatchett, Esq. F.R.S. Read December 19, 

 1 805. [Phil. Trans. 1806, p. 89.] 



No one of the resins, Mr. Brande observes, possesses so many cu- 

 rious properties as that called Guaiacum ; and he thinks it remark- 

 able, that although many of the alterations it undergoes, when heated 

 with different solvents, have been mentioned by various authors, it 

 has not excited a more particular attention. 



After noticing its more obvious properties, of which we shall only 

 repeat, that when pulverized, it is of a gray colour, but gradually 

 becomes greenish by exposure to the air, he proceeds to examine the 

 action of various solvents upon it. 



The first solvent tried by Mr. Brande was water; about 9 per cent, 

 of extractive matter was taken up, and the solution appeared also to 

 contain a small portion of lime. Alcohol, which was next tried, dis- 

 solved nearly the whole of the guaiacum, leaving only about 5 per 

 cent, of extraneous matter. The effects of water, of various acids, 

 and of alkalies, upon this solution, are then noticed. Water forms a 

 milky fluid, which passes the filter. Muriatic acid throws down an 

 ash-coloured precipitate. Liquid oxymuriatic acid forms a precipitate 

 of a pale blue colour. Sulphuric acid forms one of a pale green. 

 Acetic acid does not form any precipitate ; nor does nitric acid until 

 after the expiration of some hours, unless water be added, in which 

 case a precipitate may be sooner obtained. This precipitate is of a 

 green or a blue colour ; whereas that which forms spontaneously is 

 brc^'r 1 Alkalies do not form any precipitate when added to the so- 

 lution of guaiacum in alcohol. 



Guaiacum is less soluble in sulphuric ether than in alcohol, but 

 the properties of the two solutions are nearly similar. 



Muriatic acid dissolves only a small portion of guaiacum. Sul- 

 phuric acid forms with that substance a deep red liquid, which, when 

 fresh prepared, deposits a lilac-coloured precipitate on the addition 

 of water. The effects of nitric acid on guaiacum are minutely ex- 

 amined, of which we shall only mention, that this acid, when its 

 specific gravity was 1'39, completely dissolved guaiacum, which so- 

 lution, after standing some hours, deposited a quantity of crystallized 

 oxalic acid ; but when the nitric acid was diluted, a slight efferves- 

 cence took place, and a part only of the resin was dissolved, the re- 

 mainder being converted into a brown substance, which was similar 



