264 Dr. Marcet's Experiments and Researches [Aphil, 



A few pounds of this water were evaporated nearly to dry- 

 ness, at a gentle heat, so as to reduce the mother liquor to the 

 smallest possible quantity. This liquor was suffered to drain off, 

 and reserved for experiments, as it is in this fluid that any new 

 ingredients are most likely to be detected. 



I had suspected that some nitric salt might be found in sea- 

 water, but in this I was disappointed. The discrimination by 

 the shape of the crystals being in this instance scarcely practi- 

 cable, the mode which I employed for detecting it, consisted in 

 concentrating the bittern in a glass tube or retort, till it began to 

 deposit solid matter, then adding sulphuric acid and gold-leaf, 

 and boiling the mixture ; the gold-leaf was not in the least acted 

 upon, nor was any smell of nitric acid perceived ; but on adding 

 the smallest quantity of nitre to the same mixture, the gold was 

 dissolved, and the smell of aqua regia was instantly perceived.* 

 A portion of the said bittern was next examined by appro- 

 priate reagents, with a view to detect any minute quantity of 

 earths or metals, especially alumina, silica, iron, and copper, 

 which former inquirers might have overlooked ; but I could find 

 no other earth except magnesia : and to my surprise, I did not 

 find in the bittern the least particle of lime ; which proves that 

 sea-water contains no muriate of lime, as had been generally 

 supposed. I was equally unsuccessful in my attempts to detect 

 iron or copper, by the most delicate tests. In fact, neither alka- 

 lies nor alkaline carbonates precipitated any other substance 

 from the bittern of sea-water, except magnesia. 



The deposit obtained at Portsmouth during the early period 

 of the concentration of the water, being analyzed, I found it to 

 consist of selenite, mixed with a little muriate of soda, and a 

 portion of carbonate of lime. The presence of this last sub- 

 stance in sea-water, in a state of perfect solution, being, I 

 believe, a new fact, I neglected no means of establishing it with 

 certainty, an object which was accomplished without difficulty .+ 

 Carbonate of magnesia having been supposed by some 

 chemists to exist in sea-water, I looked for it in the same 

 deposit ; but I could not detect the least portion of it by the 

 most delicate tests/j: 



I next turned my attention to the alkaline salts of sea-water ; 

 and here I was more fortunate ; as I succeeded in ascertaining 

 beyond a doubt, that sea-water contains ammonia, as it yielded 

 sal ammoniac by evaporation and sublimation. This result was 

 easily obtained. Some of the bittern being evaporated to dry- 

 ness in a retort, and a low red heat applied, a white sublimate 



* For this easy and elegant process for detecting nitric acid, a point attended with 

 difficulty, I am indented to Dr. Wollaston. 



■f The deposit was treated with acetic acid, which occasioned an effervescence. The 

 clear liquor being then decanted off, and evaporated to dryness, and alcohol added, ace- 

 tate of lime wss found in the filtered alcoholic liquor. 



X Namely, solution of the mass in dilute muriatic acid; precipitation of the lime, 

 and addition of phosphate of ammonia to the filtered liquor. 



