Reply to a Review in Brande's Journal of Sciejice. 127 



the methods of Scheele and Vauquehn, you found them uncertain 

 in their products, and more especially in the latter case, the spe- 

 cific gravity of Vauquelin's acid always exceeding that of distilled 

 water." In opposition to which opinions, I assert, 1. That 

 Scheele's method, with common precaution, yields, by far, the 

 most equable and the purest acid for medicinal purposes, of a 

 specific gravity inferior to that quoted by you as the density of 

 the acid prepared according to your own formula, and which is 

 stated to be 0.995, although I have found it to be as high as 

 0.99S in two specimens procured at the Hall a few weeks back — 

 whereas, 0.993 is the invariable deiisitv of Scheele's acid at an 

 uniform temperature. 2. That by Vauquelin's method, prussic 

 acid, possessing all the requisite physical and medicinal proper- 

 ties, colourless, transparent, and of the specific gravity cf 0.9{;8, 

 and, consequently, under the standard density oi distilled water, 

 can he procured — i.^ annually procured to a large amount by the 

 French chemists, who sell no other — and has been procured by 

 me at two different times, since your assertion to the contrary 

 has been published by the reviewer. You have not, I su])pose, 

 forgot, that, on the evening of the 18th ultimo, 1 showed you, at 

 the table of the Royal Society, a specimen of the acid so prepared 

 by me, as well as another, prepared, according to Scheele's pro- 

 cess, by Mr. Garden, which you admitted to be " as good spe- 

 cimens as could be desired, and the purity of which, to judge of 

 their specific gravity marked on the phials containing them, 

 seemed to be quite unobjectionable." It was on that same oc- 

 casion, that I remarked to you, that the accuracy of Vauquelin 

 was too well established, to allow us for a moment to suppose, 

 that he would have recommended a process which, according to 

 your expressed opinion, " is uncertain in its products," and the 

 specific gravity of which " is «/it;ays greater tiian that of distilled 

 water." To the justice of this remark you then assented. The 

 specimens alluded to were shown that same evening, and in the 

 same place, to Dr. Holland and Messrs. Philips and Faraday, to 

 whom, as well as to you, I exhibited two other specimens of the 

 acid procured at Apothecaries' Hall in lS19and 1820. One of 

 these presented a fluid of a dark-brown colour — turbid, when 

 shaken — but transparent when suffered to rest so as to give time 

 for a copious blacki-,h sediment to subsifie : the other offered a 

 fluid of a muddy colour and appearance, though by no means so 

 striking as in tiie former case. From these two s|)ecimcns, ob- 

 tained at two different jjeriods fiom the Ihill, 1 then declared to 

 you, and to the other gentlemen ai>ovo mentioned, what I again 

 repeat on the |)rescnt occasion, that the description of the Apo- 

 thecaries' acid, contained in the second edition of my work, was 

 taken ; and I may, I think, call upon you to say, whether under 



such 



