206 Dr. Clarke on the [Oct. 



colour. By means of nitric acid the sorbic is converted into the 

 oxalic acid ; nitrous gas and carbonic acid are disengaged. 

 From this, as well as from its properties generally, M. Vauquelin 

 concludes that the sorbic acid is the one which approaches the 

 most nearly to the malic. 



For the purpose of analyzing the sorbic acid, the deutoxide of 

 copper, and the sorbate of lead, both well dried, were heated 

 together in the apparatus contrived by Prof. Berzelius. One 

 gramme (15-444 grs.) of the sorbate of lead were mixed with 

 five times its weight of the oxide of copper ; and two grammes 

 (30888 grs.) more of the oxide were used to cover the mixture. 

 One hundred and seventy cubic centimetres of gas were pro- 

 cured, which being totally absorbed by potash must have been 

 carbonic acid. The loss of weight in the apparatus was 800 

 milligrammes. The quantity of acid contained in the sorbate of 

 lead must have been, according to this analysis, 330 milligrammes. 

 From these data we learn, that the sorbic acid is composed of 



Hydrogen 16-8 



Carbon 28*3 



Oxygen 54-9 



10(H) 



With respect to the relation which the constituents of the acid 

 bear to each other, they appear to be nearly as the numbers 

 one, two, and three. The relation which exists between the 

 quantity of oxygen in the acid and that of the bases which it 

 gaturaies is as four to one. As the pure sorbic acid appears to 

 be without odour and without colour, and of an agreeable flavour, 

 the author suggests that it might be substituted for the tartaric 

 and citric acids in medicine and the arts. 



Article VII. 



On the colouring Constituent of Roses, and of the Flowers and 

 Leares of other vegetable Bodies. In a Letter to the Editors. 

 By Edward Daniel Clarke, LL.D. Professor of Mineralogy 

 in the University of Cambridge, See. 



{Continued fiom No. II. Vol. xii. p. 128.) 

 GENTLEMEN, 



In the conclusion of the thirteenth article of your number for 

 August, 1 promised to continue my observations upon the 

 colouring constituent of vegetables, and to ascertain, if possible, 

 whether ihis principle ought in every instance to be ascribed to 

 iron. The presence of iron in those bodies will, perhaps, appear 

 to be evident when i have communicated the result of a few 



