298 Mr. Schweitzer ow a7i Analysis of the 



A portion of the water was concentrated by evaporation 

 and divided into two parts ; one of which, on being treated 

 with fresh starch-paste and nitric acid, gave indication of 

 iodine ; the other part, when freed from iodine by nitric acid 

 and aether, was mixed with a solution of chlorine and aether, 

 which proved the existence of bromine. Nitrate of silver added 

 to the mineral water gave a precipitate of chloride of silver, 

 which became gray and afterwards purple, indicating organic 

 matter, which was obviously demonstrated by the residue, 

 after evaporating some of the water to dryness, becoming 

 charred during ignition. Acetate of lead gave a yellowish- 

 white precipitate, proving the absence of hydrosulphuric acid. 

 Caustic soda disengaged ammonia in abundance, which was 

 evinced even by carbonate of soda. 



The ingredients, which are present in very small quanti- 

 ties, were determined during the quantitative analysis, where 

 a large volume of the water is evaporated, and consequently 

 their detection rendered more easy. 



It may not be irrelevant to mention an excellent test for nitric 

 acid, when accompanied either by iodine or bromine, or both, its 

 value being enhanced by the following results made respecting 

 its action. It is known that the presence of nitric acid is easily 

 indicated, when, to the concentrated fluid to be examined, pure 

 sulphuric acid is added, and to this mixture a concentrated 

 solution of the proto-sulphate of iron. The smallest trace 

 of nitric acid, even the Tpo^oth or joVo^^ P^^'^' ^^ evidenced 

 by the appearance of a pink colour, more or less intense. A 

 large amount of nitric acid is indicated by a black colour, a 

 combination of the oxide of nitrogen with the protoxide of 

 iron ; however, here we have only to consider minute propor- 

 tions. The salts of iodine and bromine, when treated with 

 the same test, tinge the fluid with their own peculiar colour, 

 but a greater addition of the solution of the proto-sulphate of 

 iron destroys the colouring, which is not the case with nitric 

 acid. If the quantity of nitric acid be very small, and that of 

 iodine predominates, it is necessary for comparison to make a 

 standard fluid, from which not only the presence of nitric 

 acid may be inferred with certainty, but even its approximate 

 quantity. For that purpose I employ 50 grs. of distilled 

 water in which half a grain of iodide of potassium is dissolved, 

 to this I add gradually 50 grs. of sulphuric acid, and after- 

 wards 50 gfs. of a concentrated solution of pi'oto- sulphate of 

 iron. The sulphuric acid precipitates the iodine, which is 

 redissolved by the addition of the iron solution — forming an 

 iodide of iron — whereby the fluid assumes a yellowish tinge, 

 resembling the colour of a solution of chromate of potassa ; 



