SCIENTIFIC NKWi. y'^, 



air under a pressure of 0-76 m. [29*9 inches], and in the la- dry air, 



tidude of 45°, r: 0-00129918 of the density of water at the 



temperature of melting ice, under; equal circumstances, and 



— O'Ot 12770 of water at its greatest density. The specific 



gravity of mercury is 13-59925 at the former standard, and and mercuiy, 



13-59655 at the latter. 



The plant that furnishes gum ammoniacum is not known, Plant tliat pr»- 

 but it was supposed to be of the umbelliferous kind from ammonh^sk 

 the seeds frequently found mixed with it. Mr. Willdenouw 

 however has been so fortunate as to get the seeds to germi- 

 nate, and of the plant produced he has made a new genu8» 

 calling it heraclenm gummiferum. As the root of this plant 

 however contains no milky juice, he thinks we cannot yet « 

 consider it as certainly the plant that produces the ammo- 

 niacum. 



Mr. Suersen has given the following mode of preparing Mode«f pre- 

 benzoic acid. Boil four ounces of benzoin in powder with ^""s ocuzuk 

 three drachms of carbonate of soda in a sufficient quantity 

 of water for an nour. T.ke out the benzoin, powder it 

 afresh, and boil it again for half an hour in the same liquor. 

 After several alternr.ie bo.iings u.id powderings the soda will 

 be entirely saturated with it, and five drachms of very pure 

 benzoic acid may be precipitated from it by means of sul- 

 phuric acid ; which is at the rate of 2 J ounces from a pound, 

 or nearly one sixth. 



Mr. Rose had observed, that castor oil was completely so- Castor o'i sa* 

 luble in alcohol. Mr. Bucholz has confirmed this, and J^j'^ ^"^ ^^''^^ 

 says they unite in any proportion. Hence its sophistication 

 wiih any fat oil may readily be detected ; for these, though 

 not completely insoluble in alcohol, do not mix with it ex« 

 eept in very small quantities. Thus 60 drops of alcohol 

 dissolves drops of oil of almonds, 2 of poppy oil, 1 of rape 

 oil, and 3 of old linseed oil. With the assistance of heat 

 they would dissolve more. 



Dr. Buxton's spring course of Lectures on the Theory j^^^- , , 

 and Practice of Medicine will be commenced about the tures. 

 middle of January, 1810, at the Medical Theatre, London 

 Hospital* 



