1869.] Chemistry. 273 



appeared that the Enghsh galls were about two-thirds the value of 

 the foreign ones, or, according to the present market value, they 

 were worth about QQs. a cwt. The galls, even when in great num- 

 bers, do not appear to injure the trees. The proper time to collect 

 them would be the middle of September, when the flies have all 

 eaten their way out and laid their eggs for another year's supply. 

 In the plantations where these galls abound, a man might collect 

 easily half a cwt. in a day. 



A not uncommon adulteration of glycerin is to mix sugar and 

 dextrin with it. These substances have not hitherto been easy to 

 discover when mixed with the glycerin ; the following process is, 

 however, said to answer perfectly : — To 5 drops of the glycerin to 

 be tested, add 100 to 120 drops of water, 3 to 4 centigrammes 

 of ammonium molybdate, 1 drop of pure nitric acid (25 per cent.), 

 and boil for about a minute and a half. If any sugar or dextrin is 

 present, the mixture assumes a deep-blue colour. 



The abominable odour of bisulphide of carbon is a great bar to 

 its employment in the arts. This, according to M. Millon, can 

 soon be got rid of. The sulphide of carbon is first washed several 

 times with distilled water, as in the purification of ether, and then 

 transferred to a retort of large capacity containing quick-lime. 

 After twenty-four hours contact the sulphide is distilled off from 

 the lime, and received in a flask partially filled with copper turnings, 

 previously roasted to remove all traces of fatty matter, and after- 

 wards reduced by hydrogen. The hme remaining in the retort is 

 strongly coloured. All the disagreeable odour of ordinary bisulphide 

 of carbon is removed by this treatment, and when the nose is placed 

 close to the mouth of the receiver, an ethereal odour is only 

 perceived. With bisulphide of carbon thus purified, MM. Millon 

 and Commaille have separated the perfume of milk to the extent of 

 recognizing certain plants eaten by the cow — the Simjrnium 

 olusatrum among others. 



Professor A. Silvestri, of the University of Catana, has recently 

 discovered a great quantity of citric acid in the fruit of the 

 Oyphomandra hetacea, a plant belonging to the family of Solanacese 

 which is found here and there in the gardens of Sicily. It is 

 indigenous to Mexico, and has spread itself into Peru and other 

 parts of South America, where it is called Tomafe de la paz. It is 

 a woody plant, and attains to the height of 4 metres. On analysis 

 the fruit gives from 1 to 1*5 per cent, of pure citric acid. This 

 acid, which probably exists also in our edible tomato, has already 

 been discovered by Bertagnini in the potato, and will doubtless 

 be found in all plants belonging to this tribe. 



A plan of testing the strength of acetic acid, likely to be of 

 great use to photographers and others, has been published in 



