1835.] on Spirits. 263 



The result of these experiments on the gravities above 

 proof must be considered highly satisfactory, as evidence of 

 the correctness of the instrument in this part of its scale ; 

 the differences not being greater, than may be allowed to 

 proceed from inaccuracies unavoidable almost in performing 

 such experiments. Below proof, on the other hand, the 

 difference becomes more considerable than can be accounted 

 for in this way , the error apparently increasing with the 

 specific gravity of the spirit. 



The instrument employed was wet, for the first time, in 

 these experiments, after being received, warranted, from 

 the hands of the maker ; we have no reason to suppose, 

 therefore, any accidental inaccuracy in it or its weights. 



In each experiment, the specific gravity of the spirit was 

 accurately taken, and, in the above table, to allow every 

 thing in favour of the instrument, we have given that 

 which came nearest the indication : hence, the difference, as 

 deduced from the table, is less than a mean of the experi- 

 ments would have given. 



It may, indeed, be said that the error is as probably in 

 our tables of the composition of spirits, as in the instrument ; 

 the result of the following experiments, we think, prove 

 decidedly that this is not the case : 



One part, by measure of proof spirit, was mixed with two 

 parts of water, well shaken, and allowed to stand twenty- 

 four hours ; it is obvious that, supposing no condensation 

 to have taken place, the mixture was exactly 66-666 under 

 proof; but, from the effect of the condensation, would, in 

 reality, be a little less than this, or 66*5. 



The instrument, on trial, gave 68*9. The same experi- 

 ment was repeated, with exactly the same result, though, 

 by the weighing bottle, a sensible difference could be 

 detected in the specific gravity. 



The two mixtures were united and well shaken; the 

 hydrometer still indicated the spirit as exactly 68*9 u. p. 

 The specific gravity of this latter mixture, by a mean of 

 several trials, was -97688 at 60°, which, by calculation, 

 gives 66*533 as the per centage of the spirit, certainly very 

 near the truth. 



A mixture of 25 parts of proof spirit and 75 of water, 

 was found to be indicated by the hydrometer as 77*6 u. p 



