108 Dr. Prout on the ultimate Composition 



that the hydrogen and oxygen exist in it in the proportions in 

 which they form water. Some experiments which I made 

 many years ago appeared to render this probable; but from the 

 difficulties attending the analysis of this acid, and the uncer- 

 tainty arising from the properties of the oxide of copper formerly 

 stated, I was unable to satisfy myself completely on the sub- 

 ject. On repeatedly burning, however, a very fine specimen 

 of the acetate of copper, in a given bulk of oxygen gas, with 

 the apparatus described at the commencement of this paper, 

 it was found that the volume of the gas underwent no change, 

 and hence, that the above opinion was correct. 



Acetic acid, freed from non-essential water, I find to be com- 

 posed of Carbon 47 '05 



Water 52*95 



results which almost exactly agree with those of other che- 

 mists. 



Sugar of Milk. 



The sugar of milk employed in these experiments was pre- 

 pared by myself in the usual manner, and rendered as pure as 

 possible by repeated crystallizations. It was then freed from 

 its hygrometric moisture by confinement under a receiver with 

 sulphuric acid, and was found to consist of 



Carbon 4-0 



Water 60 



results almost exactly agreeing with those of Berzelius. 



Manna Sugar. — The saccharine principle existing in manna 

 has been long known to possess peculiar properties. That 

 employed in the following analysis was separated by means of 

 alcohol in the manner commonly described in chemical books, 

 and was obtained in a state of perfect purity by repeated cry- 

 stallizations from that fluid. It was then dried at 212°, and 

 in this state was found to consist of 



Carbon 38*7 



Water 61*3 



results very different from those of M. Theodore de Saussure*. 

 This sugar seems to part with hygrometric water only at the 

 temperature of boiling water; but a few degrees above this 

 point it begins to suffer decomposition, and at 250° it assumes, 

 without melting, the form of a brown powder, and acquires a 

 strong empyreumatic odour. 



Gum Arabic. — A very fine specimen of gum arabic reduced 

 to powder, and analysed as it existed under the ordinary cir- 



* See Bibliotheque Britannique, 1814; also Annals of Philosophy, vi. 424. 



cumstances 



