MINERAL WATERS. 



383 



ter to dryness, and adding muriatic acid to the residue. 

 If silica be present, it will be left undissolved, and will, 

 when mixed with a small quantity of soda, and subject- 

 ed to a strong heat, form a glass ; if the quantity of so- 

 da be greater, the substance formed will be soluble in 

 water, and the solution on the addition of an acid will 

 deposit the silica. 



53. Iron is very easily delected in mineral waters. 

 The triple prussiate (ferro-cyanale) of potassa when 

 added to the solution of a salt of iron, gives a blue pre- 

 cipitate. This, however, does not take place, if the 

 water contain any uncombined alkali. If this be pre- 

 sent, therefore, it must be neutralized, before adding 

 the prussiate. If the iron also be in the state of pro- 

 toxid, which is seldom the case, the precipitate is white; 

 it is necessary, therefore, in some instances, before 

 , the p'ussiate, to add a small quantity of muriatic 

 acid, by w.iich the protoxide will be converted to per- 

 oxide, and will give the blue precipitate with the prus- 

 state. 



Some have objected to this test, as the pruwiate it- 

 self contains iron, and if not carefully prepared, will 

 give a blue precipitate when added to a mineral water, 

 which contains an uncombined acid, even though iron 

 be not present. This source of fallacy may be obvia- 

 ted, by ascertaining if the pruiate give* a blue tinge 

 to diluted muriatic acid. If it d >, it must be success- 

 ively crystaiiizeil, till it does not give the blue colour 

 with the acid ; it may then be employed as an accurate 

 test of the presence of iron. 



Infusion of nutgall* is another very delicate test of 

 iron. When this is added to a mineral water, contain- 

 ing a salt of iron with the protox-d, the fluid acquires a 

 dark colour. This test is so delicate, that if one grain 

 of the sulphate be dissolved in fifteen gallons of water, 

 the solution will acquire a dark tinge on the addition 

 of the infusion. In thi* case, however, the blackness 

 does not appear for some days. 



The colour produced by nutgalls, and the delica- 

 cy of it as a test, are affected by the presence of other 

 substance*. An earthy carbonate make* the test much 

 more delicate ; thus the infusion will detect a minute 

 quantity of iron when dissolved in common well-water, 

 which contains carbonate of lime, but will not indicate 

 its presence, when dissolved in the same quantity of 

 diitilled water. An alkaline carbonate makes the co- 

 lour dark violet, and, if sulphate of lime be present, the 

 Kecipiute is at firt white and afterwards becomes 

 ck. 



.j >-. ' '""per may be detected by evaporating the fluid 

 to drynesi, dissolving the residue in nitric acid, and 

 Adding ammonia to the solution. If this metal be pre- 

 sent it will acquire a blue colour. 



Qf ike Method* employed in atcerlaining thr quantity of 

 the different ingredient! in Mineral Waltrt. 



of the mr . 55. To ascertain the quantity of the oxygen, nit: 

 '** *' and carbonic acid which water contains, the method al- 

 ready mentioned for ascertaining the nature of the elas- 

 tic fluids must be followed. (3<i.) The quantity of oxy- 

 q.'mjtrof g en w '" be known by the use of the solution of thesiil- 

 ihedifTr- p-iuretteil hydro-sulphuret of potassa, that of the car. 

 . - oonic ncid liy means of potassa having previously re- 

 liirntt in moved the sulphuretted hydrogen by the addition of 

 nitric ncid to the water in the jar. If the elastic fluid 

 contain inlphurotu acid, iti quantity will be ascertained 

 by introducing the peroxid of lead ; the amount of the 

 absorption -. the test for each will indicate 



it* proportion following the usual precautions of bring. 



6 



ing the elastic fluids to the mean temperature and pres- Mineral 

 sure. Waters. 



56. The quantity of sulphuretted hydrogen cannot be '>'' 

 found out by boiling the fluid, as the whole of the gas 

 is not in this way expelled. The method recommended 

 by Kirwan, is to fill three-fourths of ajar with the wa- 

 ter, and invert it in a water trough ; then throw up 

 nitric oxide, as long as red fumes appear. By this the 

 sulphuretted hydrogen is decomposed, and the sulphur 

 is deposited. This must be collected, and dried with 

 a gentle heat. Each grain of it indicates 8 cubic inches 

 of sulphuretted hydrogen. 



The quantity of the saline ingredients in a mineral 

 water may be ascertained either by finding its specific 

 gravity, or by evaporation. 



Mr. Kirwan has given an easy rule, by which we can 

 ascertain the proportion of the saline matter by the spe- 

 cific gravity of the fluid. The specific gravity of dis- 

 tilled water must be subtracted from that of the mine- 

 ral water, and the remainder must be multiplied by 

 1.4. The product is the quantity of saline matter, in a 

 quantity of the mineral matter, equivalent to the num- 

 ber denoting the" specific gravity of the distilled water. 

 I hii-, suppose the specific gravity of distilled water 

 1000, and that of the mineral water 1 100, then 1 100 

 1000x1.4=140.00 and 1000: 140.00:: 100: 14.000; 

 the fluid therefore contains 14 per cent, of saline mat- 

 ter, supposing this free of its water of crystallization. 



1 lu- other met IKK! of ascertaining the quantity 

 of saline matter, it to evaporate slowly by heat, a cer- 

 tain quantity of the fluid to dryness, and expose the re- 

 sidue to a temperature sufficient to drive off the whole 

 of the water; the residue indicates the quantity of sa- 

 line ingredients. 



59- Smlpkuiic acid. The quantity of sulphuric acid 

 present is ascertained by exposing to a red heat the 

 precipitate given by baryta (4) ; lOOgr. of it are equi- 

 valent to 34 of real sulphuric acid. 



60. Boracic acid. To find the quantity of boracic acid, 

 add sulphuric acid to the prct ipit.itc yiwn with the 

 acetate of lead (44,) filter the fluid, and evaporate it t<i 

 dry net*. Dissolve the residue in alcohol, and again 

 evaporate. The residue is boracic acid. 



61. Muriatic ncid. The quantity of muriatic acid is 

 known by igniting the precipitate afforded by the salt 

 of silver, (43) ; lOOgr.ore equivalent to 19 of muriatic 

 ncid. 



62. Lure. The proportion of lime is ascertained by 

 drying by a gentle heat the precipitate thrown down by 

 oxalic acid (48), 100 gr. = 44 lime. Or, the precipi- 

 tate may be exposed to a high temperature, and then 

 converted to sulphate by the addition of sulphuric 

 acid. 100 gr. of this, after ignition, are equivalent to 

 41.5 lime 



63. Magnuia and alumina. By boiling in potas- 

 sa the precipitate of magnesia and alumina thrown 

 down by potassa, (5fi) the magnesia will be left, and 

 aftrr being washed and dried, must be weighed. By 

 adding muriatic acid to the solution of the alumini, 

 and then sub-carbonate of potass*, the earth will be 

 precipitated. It must be washed, exposed to a red 

 heat, and weighed. 



64. Iron. Different methods are recommended for 

 ascertaining the quantity of iron or its oxides. 



Some chemists have objected to the prussiate of 

 potassa, as an accurate method of indicating the qiinn- 

 tityofiron, as this salt itself contains iron, which H 

 thrown down and forms part of the precipitate. This 

 source of error may be avoided, by ascertaining the 



