384 



MINERAL WATERS. 



Of the me- 

 thods fol- 

 lowed for 

 ascertain- 

 ing the 

 state Of 

 combina- 

 tion in 

 which the 

 different 

 ingredients 

 exist in mi. 

 eral wa- 

 ters. 



quantity of iron that a given -weight of the prussiate, 

 carefully prepared, (53) contains. This is done by 

 exposing 100 grains of it to heat, in an open vessel, by 

 which the oxide of the metal is obtained. In using this 

 test then, to find out the quantity of iron in the mine- 

 ral water, the quantity of prussiate employed must be 

 ascertained, and the weight of the oxide, which this is 

 known to contain, must be subtracted from the weight 

 of the precipitate. 100 grains of the blue precipitate, 

 dried by a gentle heat, according to Porret =34%23 

 per oxide of the metal. 



Another method of ascertaining the quantity of iron, 

 is to bring the metal to a high state of oxidation, by 

 exposing it for some time in an open vessel, to a strong 

 heat, in which condition it is insoluble in nitric acid. 

 By pouring this acid on the residue, the oxide of iron 

 is left, while the other substances are dissolved. 



Of the Methods followed for ascertaining the state of 

 Combination in which the different ingredients exist in 

 Mineral Waters. 



Very different opinions are entertained with respect 

 to the state of combination in which the different 

 ingredients exist in mineral waters. Some chemists 

 suppose that they form binary compounds ; others, on 

 the contrary, imagine, that they are all more or less unit- 

 ed with each other. Thus if there be an acid, an alkali, 

 and an earth together, it is not supposed that these are 

 in the state of binary compounds, forming a salt of 

 the alkali and another of the earth, but that they are 

 combined so as to form a triple salt. The former is 

 the more prevalent opinion. Some chemists assert al- 

 so, that the salts procured by the evaporation of the 

 fluid, are those which exist in solution, while others 

 maintain, that during the evaporation new compounds 

 are formed, so that we do not by this means procure 

 those which the water in its natural state contains. 

 This assertion is strengthened by the fact, that some 

 salts exist together in solution, when much diluted, 

 which decompose each other when the solution is con- 

 centrated. During the evaporation of a mineral wa- 

 ter, therefore, new affinities may exert their influence, 

 and salts, different from those which exist in the water, 

 may be obtained. The experiments of Dr. Murray, 

 immediately to be stated, tend to confirm this opinion. 

 According to the different opinions which are en- 

 tertained, with respect to the state of combination of 

 the ingredients, different methods have been recom- 

 mended for ascertaining the compounds which mineral 

 waters contain. The first of these is by the slow eva- 

 poration of the fluid. 



By slowly evaporating the water, the different saline 

 substances may be obtained separately. For this pur- 

 pose, the evaporation is continued till a pellicle ap- 

 pear on the surface ; the liquid is then allowed to cool 

 slowly ; by this the earthy carbonates will be deposit- 

 ed. After these are removed, by a farther evaporation 

 and cooling, the sulphate of lime will be separated. 

 The alkaline neutral salts, and the sulphate of magne- 

 sia, will be deposited after the next evaporation. The 

 muriates of lime and magnesia will remain, and will 

 be obtained by evaporation to dryness. 



If the water contain carbonate of iron, it must, after 

 having been evaporated to a certain extent, be exposed 

 to the air, by which the iron passes to a higher state of 

 oxidation, and is no longer soluble in the acid ; it is 

 therefore precipitated. The earthy carbonates are 



likewise separated by this means. After these have 

 been deposited, the fluid may be evaporated to dry- y 

 ness, and a small quantity of water poured on the re- 

 sidue, by which some of the salts will be dissolved, 

 and the others will be left. Sometimes the water is 

 evaporated to dryness, and the residue is expospd to 

 the air, by which the deliquescent salts, as the muriates 

 of lime and magnesia, absorb moisture, and are dissolv- 

 ed. What is left undissolved, may be afterwards sub- 

 jected to the action of water. Occasionally after eva- 

 porating the fluid to dryness, the residue is subjected 

 to the action of successive portions of water, by which 

 the salts are taken up in the order of their solubility. 



The different quanties of saline substances, thus ob- 

 tained by these various methods, must be dissolved in 

 separate portions of water, that by slow evaporation 

 the salts which are mixed may be separated. 



Another method of ascertaining the nature of the 

 salts in mineral waters, is by means of alcohol. Some 

 of the salts contained in mineral waters are soluble, 

 while others are insoluble in alcohol. By a particular 

 management, the different saline substances may be 

 obtained, either in solution, or by deposition from the 

 water. 



When alcohol is added to water, containing saline 

 matter, the attraction between the two fluids is so 

 strong, that those salts which are insoluble in alcohol, 

 are separated from the water, and are deposited ; thus 

 if a mineral water be mixed with an equal quantity of 

 alcohol, sulphate of lime, if present, will be precipi- 

 tated : if more alcohol be added to the fluid, the sul- 

 phate of soda will be separated ; by adding another 

 quantity of alcohol, muriate of soda will be thrown, 

 down. This method of employing alcohol in the 

 analysis of mineral waters, was first pointed out by 

 Boulduc. 



Lavoisier has recommended another way of using 

 alcohol. For this purpose the mineral water is to be 

 evaporated to dryness, and eight parts of alcohol 

 poured on the residue, by which some of the salts only 

 will be dissolved. By adding alcohol, diluted with a 

 little water to the undissolved matter, another portion 

 of the saline substance is taken up. In this way, by 

 using alcohol of different specific gravities successively, 

 the different saline compounds may be obtained se- 

 parately ; thus when strong alcohol is poured on the 

 residue of the evaporation of a mineral water, mu- 

 riates of lime and magnesia, if present, will be dissolv- 

 ed. By diluting the next portion of alcohol with a 

 little water, muriate of soda will be taken up, the car- 

 bonates and sulphates being left. 



Occasionally these two methods of employing alco- 

 hol are joined ; thus the mineral water is evaporated 

 to dryness, and alcohol is poured on the residue, by 

 which the muriates of lime and magnesia are dissolved. 

 When the solution is completed, the fluid is filtered, 

 and a small quantity of cold water is added to the un- 

 dissolved matter, by which more of the saline sub- 

 stance is taken up. What remains is then boiled in a 

 large quantity of water; by the application of the tests 

 to the alcoholic and watery solutions, the differeut 

 Substances which they contain will be discovered. 



It is supposed that considerable information may be 

 derived with respect to the composition of mineral 

 waters, from the knowledge of what are called incom- 

 patible salts. When a certain class of salts have been 

 procured from a mineral water, it is generally inferred 

 that other salts of a peculiar nature do not exist in 



