171 the English Channel near Brighton, 57 



corresponding quantity of ammonia, which kept the chloride 

 of silver in solution, will be free and act upon the bromide of 

 silver ; but by observing the before-mentioned precaution, 

 every error of that kind will be avoided. Should a fluid con- 

 tain iodides and bromides without chlorides, and not in too 

 small a proportion, a very good method of ascertaining their 

 respective quantities is to precipitate them at once with 

 nitrate of silver, and to heat the dry precipitate in an atmo- 

 sphere of bromine. 1 have found, when iodide of silver is 

 melted in an atmosphere of bromine, it is entirely changed 

 into a bromide ; and from the difference of the weight between 

 the mixture of iodide and bromide of silver, and that of the 

 whole bromide of silver, the respective quantities of iodine 

 and bromine may be ascertained. Thus the quantity of 

 iodine (or bromine) stands in proportion to the difference of 

 the weight, as the atomic weight of iodine (or bromine) is to 

 the difference of their atomic weights. Hence it would only 

 be required for the quantity of iodine to multiply the given 

 difference of the weight by 2,627, and for that of bromine to 

 multiply it by l5()27. Professor H. Rose, of Berlin, applies 

 a similar method for the separation of iodine from chlorine. — 

 (Poggendorff's Ann. 1834, No. 37, p. 583, 584.) 



I may appear to have dwelt long upon this subject, but the 

 importance into which brine springs have arisen on account 

 of their powerful components, iodine and bromine, has induced 

 me to examine the matter closely, as it maybe of consequence 

 to the medical profession to know the exact quantity of these 

 valuable substances. 



I have briefly to add, that the quantity of chlorine in sea- 

 water was ascertained by means of nitrate of silver, deducting 

 from it that proportion of bromine which had been found 

 according to the foregoing method. The quantity of sul- 

 phuric acid was found by chloride of barium, the water having 

 previously been mixed with a little nitric acid. Another 

 portion of the water was mixed with chloride of barium with- 

 out the addition of an acid, when the difference of the weight 

 between this and the former precipitate gave the amount of 

 carbonate of barytes from which the proportionate quantity of 

 carbonic acid gas was computed ; its quantity was likewise 

 ascertained after the distribution of the acids amongst the 

 bases, when the surplus of the lime or of one of the other bases 

 must have been united to carbonic acid. The quantity ob- 

 tained by analysis was a little less than the last, owing to the 

 carbonate of barytes not being entirely insoluble in water 

 during lixivation. Lime was separated by oxalate of ammo- 

 nia, the water having been previously mixed with a proper 



