Page:Proceedings of the Royal Society of London Vol 1.djvu/236

Rh 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 sguare of the velocity of a body in which such force is ac- cumulated.

No one of the resins, Mr. Brande observes, possesses so many on- 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 he sooner obtained. This precipitate is of a green or a blue colour; whereas that which forms spontaneously is hm:-, 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. Sulphuric 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 examined, of which we shall only mention, that this acid, when its speciﬁc gravity was 1‘39, completely dissolved guaiacum, which solution, after standing some hours, deposited a quantity of crystallized oxalic acid; but when the nitric acid was diluted, a slight effervescence took place, and a part only of the resin was dissolved, the remainder being converted into a brown substance, which was similar