VOL. XXXIII.] PHILOSOPHICAL TRANSACTIONS. 121 



periment, they can distinguish not only French brandy from malt spirits, but 

 likewise what is genuine from adulterated brandy; and that consequently they 

 cannot be imposed on in buying the genuine sort. Hence it is still considered 

 as an infallible proof, and as a grand secret : so that M. Neuman could not 

 procure, either to smell or taste this proof-liquor. 



This liquor is of a duskish yellow tincture; and with it the experiment is 

 made in the following manner; first they fill a glass with the brandy to be 

 proved; and into this glass they put 1, 2 or 3 drops of that liquor, more or 

 less, according to the quantity of brandy used; and if the brandy be good and 

 genuine, there immediately appears at the bottom of the glass, a very beautiful 

 blue colour; which, if stirred, and well mixed with the rest of the brandy, 

 tinges it entirely of an azure ; but if it be malt spirit, there is no such tincture 

 to be seen in the glass, this retaining its pristine tincture, though 20 times the 

 number of drops be put into the glass. Therefore as this method of proving 

 does, according to the opinion of the merchants, generally serve to distinguish 

 pure malt spirits from pure French brandy ; so, depending on this hypothesis, 

 they judge of the different degrees of the adulteration of brandy and malt 

 spirits; for, they pretend to judge, from observing the blue colour, unless it 

 be obscure, but provided it be a bluish gray or a bluish green, that the 

 brandy is not only adulterated, but likewise with what proportion of malt spirits, 

 more or less, it is mixed. 



At first Mr. N. took this to be a certain and infallible method of proof. — 

 But considering that no demonstrative experiment had hitherto been made, by 

 which we might show, or at least suspect, the peculiar constituent parts of pure 

 French brandy, distinct from malt spirits, equally rectified; but that both 

 consist of the same essential parts; to which common quality they are simply 

 reduced by necessary fermentation ; he therefore thus reasoned with himself; 

 that if any remarkable difference happened in the spirits, it was owing, neither 

 to the intimate composition that constitutes the brandy itself, nor to the nature 

 of the wine from which it is distilled, but necessarily arises from some hetero- 

 geneous additament, no ways constituting brandy, as such ; whether it be added 

 in fermentation or distillation ; or whether it happen by tinging, extracting, or 

 even by the commixture of other liquid or soluble bodies. 



M. Neuman would not acquiesce in such thoughts alone, for the most part 

 precipitate and fallacious; but made several experiments to that purpose; by 

 which he easily had a confirmation of his conjecture, namely, that that appa- 

 rent difference, by means of the above experiment, is in no manner a true and 

 essential distinction of spirits ; but that the production of the blue tincture, by 

 which the difference is judged, is owing to some heterogeneous additament, 



VOL. VII. R 



