Imágenes de páginas
PDF
EPUB

some of the metallic oxides possess of paintings, and the oxygenated water separating the oxygen is curious.- does not in general injure those other When these are added to it, the oxy- colours with which the white lead is gen flies off with a sudden explosion: in contact on the canvas. It is said, and, what is more, the oxygen of the however, that the same property is oxide itself is liberated along with it, possessed also by chlorine, a substance and the metal is reduced to a state of much more easily procured. purity. Another singular fact is, that even the pure metal, when thrown into oxygenated water, effects a separation of the oxygen. In order to CONSTITUTION AND ANALYSIS OF account for such an agency in a sub

MINERAL WATERS. stance which does not enter, in the meantime, into any new chemical Chemistry, in some of the improvestate, M. Thenard sagaciously sug- ments which it has recently undergests that the agency of the metal gone, has acquired a more complicamust be of an electrical nature. On ted aspect than it previously wore, this point, room is left for farther re- but in others it has been much simsearch.

plified. In both cases, the science is A question has been raised, whe- extended, and its foundations fixed in ther in the liquid oxygenated acids a more satisfactory manner. The comthe oxygen is in union with the acids, position of mineral waters has always or merely with the water? If the lat- been an object of great interest to the ter, the force of the argument already chemist as well as to the physician. stated with regard to chlorine will This has been manifested by the labe weakened, because the new com- borious manipulations which have pound, so different from chlorine, been employed in the analysis. These will come to be viewed not as an oxy- have been multiplied by the difficulty genated muriatic acid, but muriatic of the subject, and they have in geacid in combination with oxygenated neral tended to display in the end an water. As an argument for suppo- uncertainty which appeared to be insing that the oxygen is really in union separable from it. In the midst of with the acid, it has been observed much doubt and disappointment, it that simple water does not retain the is pleasing to find a ray of light thrown oxygen so powerfully as the liquid on their composition, which tends in acids do. But the force of this fact

one respect to simplify our views and diminished by another which has abridge our labours, by shewing us been discovered, viz. that various at what point an uncertainty comother impregnations, such as sugar mences which no labour is adequate and gum, also impart to water the to remove. property of retaining the combined Dr Murray's analysis of the mine. oxygen with greater power.

ral waters of Dunblane has led him Oxygenated water has been repre- to these improved views, which are sented as possessed of a property ca

unfolded in the 7th and 8th volumes pable of being turned to good prac. of the Transactions of the Royal Sotical account, viz. that of removing ciety of Edinburgh at full length, in the dark colour induced on white three Memoirs, entitled, “An Analy. lead by sulphureted hydrogen, which sis of the Mineral waters of Dunin

many cases spoils the effect of old blane;"_"An Analysis of Sea-Water;" and " A general Formula for neutralize the base. From the quanthe Analysis of Mineral Waters ;" all tity of sulphate of lime formed, that of them containing important infor. of the muriate of lime was calculated mation, both on general principles on the principles of chemical equivaand on the details of manipulation. lents.-20.5 grains of sulphate of lime It is only a statement of the impro- were obtained, leaving 16.7 of dry ved principles and general modes muriate of lime. The matter undisthus introduced that we can propose solved by the alcohol amounted to now to give, which will be most ad. 28.5 grains. This matter was found vantageously done in the order in to be all soluble in distilled water, which they are laid down, and in except 2.4, and of this .5 were found which they seem to have occurred to to be carbonate of lime, and nearly this chemist.

.2 sulphate ; but, from the quantity The water of Dunblane shewed, of sulphuric acid found by testing in the usual preliminary trials, that with a barytic salt, there were altoit consisted of neutral salts, composed gether 2.9 of sulphate of lime, proviof sulphuric and muriatic acids, lime, ded the whole of that acid which was a minute portion of iron, and pro- present existed in a state of combinabably soda, though the presence of tion with lime. He confirmed the this last ingredient is less easily sub- accuracy of the results, by executing stantiated by trials of that prelimina- an analysis by a different method, ry kind. Muriates of soda and lime, which gave in a pint of the water, with a smaller portion of a sulphate, were presumed to be the neutral salts by which it was impregnated ; and

Muriate of soda

24 grains the usual method of ascertaining the

Muriate of lime

18 individual salts, by evaporation and

Sulphate of lime

Carbonate of lime crystallization, was resorted to.- Oxide of iron

0.17 When an English pint was evaporated, 47 grains of a solid residue were

45.17 left. This, when dried and then exposed, deliquesced from the presence This water has a purgative quality, of the muriate of lime, the muriate which must arise from its impregna-of soda remaining crystallized. These tion; yet the muriate of lime is not ingredients were more completely se- known to possess that power, and parated by means of alcohol, which muriate of soda only in a very slight dissolved the muriate of lime, and left degree. This was an exemplification the muriate of soda in the state of of a well-established general fact, that crystals; and, though such separation the powers of mineral waters are of. was not perfect in the first instance, ten much greater than can be antiit was completed by means of a repeti- cipated from the nature and quantity tion of the processes of solution and of their ingredients; and that the ac. crystallization. The quantity of the tion of saline substances is increased, muriate of lime was not only ascer. and considerably modified, when they tained by driving off the alcohol which are in a state of great dilution. dissolved it, and weighing the solid This paper contains also an analymatter that was left, but by determin- sis of the water of Pitcaithly, affording the quantity of sulphuric acid re- ing the following results, as the inquired to decompose that salt, and gredients of an English pint.

[ocr errors]

.

3.5 0.5

[ocr errors]

Muriate of soda

13.4 grains.

stance apparently inert in its relation Muriate of lime

19.5

to the living system. If it exist, Sulphate of lime

0.9 Carbonate of lime

0.5

therefore, as such in the water, it

can contribute nothing to its efficacy. 34.3

But in the other state of combination With a slight trace of iron.

which is supposed, both the quantity Atmospheric air

of muriate of lime, the active ingre

0.5 Cubic Inch. Carbonic acid gas

1 Ditto.

dient, will be greater, and the pre

sence of sulphate of soda will in part The observations which the author account much better for the purgamakes on the general question,-in tive operation which the water exerts. what state do all the saline ingredients The question does not admit of being exist in a mineral water?-are of great determined by direct experiment, as importance. The different acids and we know not when a neutral salt is bases may either be supposed to ex. merely separated from a solvent, and ist in a state of simultaneous combi- when it is formed in the operation. nation, the whole acids being neutral. Nor does its separation by alcohol ized by the whole bases; or, as form- afford an unambiguous demonstraing a mixture of different neutral tion, as the alcohol may operate by salts. The latter opinion is embra- acting on the water, and diminishing ced by him as the most probable of its solvent power by withdrawing it the two: Yet he conceives that the from the dissolved substance ; thus neutral salts, existing in the water, leaving room for the force of cohemay not be the same with those which sion to act in determining the comare evolved by the process of eva- bination of those ingredients which poration of crystallization, because form the least soluble compound. the state of combination is liable to One presumptive fact, however, was be modified by the analytic opera- evolved by the author's experiments. tions themselves. For example, when He added to different portions of the muriate of soda, muriate of lime, water (four ounces each) 5, 10, 15, 20, and sulphate of lime, were obtain and 30 grains of sulphate of soda. In ed in the quantities which we have the greater number of those proporstated from the Dunblane water, it tions, the quantity of sulphate of soda is possible that the sulphate of lime was more than sufficient to convert the may have been a product of the ope- whole muriate of lime in the water ration, and not an original ingredient. to sulphate ; and, according to the The sulphuric acid may exist rather known solubility of this salt, the in the state of sulphate of soda, and quantity of water was not sufficient to when, in the progress of the evapo- retain it all dissolved. Another result ration, the liquor becomes concentra- which he obtained was, that when he ted, this salt may act on a portion of added a small portion of sulphate the muriate of lime, and by mutual of soda, the quantity of sulphate of decomposition form corresponding lime obtained was increased." When portions of muriate of soda and sul. ten grains of the crystallized sulphate phate of lime.

of soda are added to a pint of the This is not a question of mere spe water, four grains, or double the culation, but may sometimes throw quantity of sulphate of lime are oblight on the properties of mineral tained; proving that both muriate of waters. For example, in the present soda and sulphate of lime are liable instance, sulphate of lime is a sub- to be formed in the progress of the

20.8

evaporation. Though the conclusion principal interest of this view arises is not thus absolutely established, from its relation to the question, whethat the sulphuric acid exists in this ther chemical analysis is capable of water in the state of sulphate of soda, discovering the sources of the mediciit is greatly favoured by it, and is on nal virtues of mineral waters?—which the whole the most probable opinion. some have been disposed to decide in If it be admitted, the statement of the negative, from the fact that analythe ingredients and their propor- sis, in some instances, detects no ingretions must be altered; the sulphate of dients of adequate activity to the eflime must be omitted; the sulphate fects which these waters are found to of soda, though it cannot by any produce on the system. It has been method be separated in that form, always found difficult to account for may have its quantity inferred from the virtues of the celebrated Bath wa. that of the sulphate of lime, which is ter, the ingredients obtained from it formed by its acting on the muriate possessing little activity, and the prin. of lime. The sulphates of lime and cipal ones none at all. An English of soda being nearly the same in pint of it contains, along with a slight weight, the quantity found of the one impregnation of carbonic acid, nine may nearly be substituted for that grains of sulphate of lime, three grains of the other, as inferred to be present, of muriate of soda, three grains of suland the whole proportions will be: phate of soda, eight-tenths of a grain

of carbonate of lime, one-fifth of a Muriate of soda,

21 grains. grain of silica, and one-twentieth of Muriate of lime,

a grain of oxide of iron. From these Sulphate of soda,

3.7 no medicinal operation of any imporCarbonate of lime, Oxide of iron,

0.17

tance could be expected: they are

either altogether inert, or in quanti46.17

ties so extremely minute as to be in

capable of producing any sensible efThe accuracy of this statement was fect in the dose in which the water is confirmed by next adding such a pro- taken. Yet their virtues are establishportion of the sulphate of soda as was ed by sufficient practical evidence, adequate to convert the whole murie and also their injurious effects when ate of lime into sulphate.--He added certain precautions in the use of them to a pint of the water 24 grains of are neglected. To account for these, sulphate of soda, and obtained 24.8 however, various hypotheses have been grains of precipitated sulphate of lime. proposed. It has been maintained By various subordinate manipulations, that substances given in small doses, the author obtained a perfect degree in a state of great dilution, may, from of accuracy. For these, and the mi. this dilution, produce more effect on nute calculations founded on them, the general system than the quantity we must refer to his Memoir. given would lead us to expect. It

He applies the conclusions which is also supposed, that the temperature he draws to all those mineral waters of the water may have some influence, in which sulphate of lime is mention- particularly by favouring the action ed by chemists as an ingredient along of the iron. Something has been ascriwith muriate of lime and muriate of bed to the nitrogen gas rising through soda. In almost all of them, where the water, or the siliceous earth, of sulphate of lime is an ingredient, mu- which one pint contains a grain. All riate of soda is also present.--But the this is unsatisfactory. It is not easy

0.5

3.1 5.5 0.8 0.2

1

og grain.

Muriate of lime, to believe that a sixtieth of a grain

Sulphate of soda, of iron, however much favoured by

Carbonate of lime, the circumstances now mentioned,

Selica, can produce any important medicinal

Oxide of iron, effect ; and the reasoning applied to the other ingredients, instead of re

The peculiarities in the composimoving the difficulty, rather places tion of the Bath water, compared with it in a clearer light. But the view the greater number of saline mineral which Dr Murray has advanced, en

waters, is, that it contains a larger ables us to assign to the Bath water quantity of sulphate of soda than is a much more active chemical compo- necessary to convert its muriate of sition, and to ascribe its power to a

lime into sulphate of lime. Hence substance of known activity,--MURI- no muriate of lime is obtained after

of ducts of its analysis are sulphate of evaporation in its analysis ; hence

even a portion of sulphate of soda is lime, muriate of soda, and sulphate indicated; and hence the larger proof soda. The proportion of sulphate portion of sulphate of lime which that of lime is such, that part of it must analysis yields. In the Dunblane pre-exist in the water; but part of it and Pitcaithly waters, the sulphate of we are to consider as the product of soda is deficient. The muriate of lime the analysis: the muriate of soda is en is in large quantity, and is accompatirely so; and the quantity of sul- nied with muriate of soda. Hence phate of soda existing in the water, in their analysis no sulphate of soda is larger than that afforded by the analysis . Muriate of lime, sulphate sulphate of lime, but a large propor

appears, and only a small quantity of of soda, and sulphate of lime, are its tion of muriate of lime. ingredients; and during the evapora- Muriate of lime is a substance of tion, the muriate of lime being acted great activity in its operation on the on by a portion of the sulphate of living system. Quantities of it which soda, muriate of soda and a corre

are not very large prove fatal to anisponding portion of sulphate of lime mals

. Six grains of it are, according are formed. The latest, and proba- to the view now given, contained in bly the most accurate, analysis of the

a quart of the Bath water. This is Báth water, that of Mr Phillips, gives not far from the medium dose of this the following view of its composition: salt, and equal to one half of the In an English pint

largest dose that can be given in a

regular course without producing ir. Carbonic acid,

ritation; and this, aided by the state Sulphate of lime,

grains. Muriate of soda,

of great dilution favouring its more Sulphate of soda,

extensive application within the body Carbonate of lime,

and its reception into the blood by

absorption, together with the elevated Oxide of iron,

grain.

temperature of this mineral water, But considering the composition will give us a far better explanation according to the preceding view, the of its well known efficacy than any

hitherto advanced. ingredients and their proportions will

The Cheltenham water affords, by be:

analysis, sulphate of magnesia, sulCarbonic acid,

1.2 inches. phate of lime, muriate of soda, mus Sulphate of lime,

5.2 grains. riate of magnesia, carbonate of mag

1.2 inches.
9
3.3
1.5
0.8
0.2

Seleca,

[ocr errors]
[ocr errors]
« AnteriorContinuar »