on the Saline Contents of Sea-Water. 4S5 



Some time after the communication to which I have just 

 referred, an extraordinary statement was pointed out to me, 

 upon the authority of Rouelle, a French chemist of the last 

 century, fi-om which it appeared that mercury was contained 

 in sea salt*: and I saw soon after in the ^Annates du Musee, 

 vol. vii. a paper by the celebiated chemist Proust, who, in a 



great measure, confirmed that statement, by announcing that 

 e had found traces of mercury in all the specimens of marine 

 acid which he had examined. 



Improbable as the fact appeared, I thought it worth while 

 to repeat the experiment, and to lake that opportunity of 

 making some collateral researches upon other substances, much 

 moi-e likely than mercury to ba discovered in sea-water. 



For this purpose I availed myself of the kindness of my 

 friend Mr. John Barry f, who happened to be in the vicinity 

 of Portsmouth, to supply me with specimens of sea-water, 

 carefully concentrated upon the spot, in vessels of Wedgwood 

 ware, and with scrupidous attention to cleanliness ui the pro- 

 cess. Accordingly he was so obliging, as not only to send 

 me a quantity of brine evaporated under his own eye, in the 

 manner just mentioned, but he also collected for me a valuable 

 series of specimens from the salt-works near Portsmouth, from 

 all tiie stages of the process, so as to afford me an opportunity 

 of investigating with accuracy all the chemical circumstances 

 of this interesting branch of national oeconomy. Finding my- 

 self, however, much pressed by time at this late period of the 

 session, I shall, after briefly adverting to Rouelle's supposed 

 discovery, confine myself in this communication to a few ob- 

 servations which I have made on sea-water itself; keeping out 

 of view, for the present, the topic of salt-making, which, how- 

 ever, I intend to resume at some future period, in a more com- 

 plete and satisfactory manner. 



I first attempted to detect mercury in a specimen of bay-salty 

 such as is obtained in the salt-works near Portsmouth, b}' 

 spontaneous evaporation. This variety of salt forms large 

 crystals, but is always more or less contaminated by earthy 

 matter, which gives it a dirty appearance. It has, probably, 

 a general resemblance to the French Sel de Gahelle, which 

 is more impure still, though, I believe, obtained in a similar 

 manner J. 



• See Journal de Medecine, vol. xlviii. 1777, page 322. 



•f- Mr. John Barry, of Ploiiirh Court, inventor of a new and valuable 

 process for preparing extracts in vacuo, &c. 



X The name of bai/salt is often applied to foreign as well as British salt, 

 and in general it simply denotes that the salt lias been obtained by sponta- 

 neous evaporation. 



3 I 2 Eight 



