very

The composition of this water, according to this analysis, is similar to that of the Dunblane water. No account is given, however, so far as I have been able to discover, of the manner in which it had been executed, and it is therefore uncertain to what state of dryness the ingredients had been brought to which their proportions are referred. Hence no comparative estimate can be made of it with any other mineral water; and this led me to undertake its analysis, in the same manner as that of the Dunblane water.

Pitcaithly is situated in the valley of Strathern, and though at rather a greater distance from the front range of the Grampians than Dunblane, it is not improbable that the spring may have a similar origin with the Dunblane one, and may rise from the red sand-stone which appears to form the first rock on descending from the primitive rocks, and to extend over all this district.

The taste of this water is saline, and somewhat bitter. Comparing it with the Dunblane water, both being tasted at the same time, the taste of the Dunblane water is stronger, and in particular more saline than that of the other. The medicinal operation of the Pitcaithly water, in the sensible effects it produces, is diuretic and purgative.

The gaseous impregnation of the water could be examined properly only at the spring, which I had not the opportunity of doing. But having procured a quantity of the water, I submitted it to the same examination as in the preceding analysis, to ascertain its solid contents. The usual re-agents produced the following appear

ances:

1. The colours of litmus, violet, and turmeric, were scarcely affected. If there were any change, it was that of the litmus becoming more blue, and that of the violet-green; but this was so slight as to be rather doubtful. The turmeric underwent no change.

2. Muriate of barytes produced a turbid appearance and precipitation; but this was much less considerable than in the Dunblane water. The transparency was not restored by nitric acid.

3. Nitrate of silver produced a very dense and copious precipitate.

4. Water of potash gave a milkiness not very considerable.

5. Carbonate of potash threw down a copious precipitate, which disappeared with effervescence on adding nitric acid.

6. Lime-water had no sensible effect.

7. Ammonia, when perfectly free from carbonic acid, caused no turbid appearance.

8. Oxalate of ammonia produced an abundant precipitation.

9. Tincture of galls, added in a very minute quantity, did not immediately produce any effect; but after a few hours, a dark colour appeared, which gradually deepened, inclining to an olive-green. With all these tests, the general results are the same as those from the operation of the same tests on the Dunblane water. experiment 7th, the ammonia, if not perfectly free from carbonic

In

acid, produced a slight turbid appearance; and even when in its purest state, a very slight opalescent hue was perhaps apparent; but this obviously depended on the presence of a little carbonic acid; for when a drop or two of nitric acid was previously added, and the water heated, no such appearance was produced; or, if boiled strongly, without any addition of acid, on restoring the original quantity of liquid, by adding distilled water, the transparency was not in the slightest degree altered on adding pure ammonia. The slight precipitate, too, which did occur in any case was dissolved by the most minute quantity of muriatic acid with effervescence; and this solution became turbid on adding oxalate of ammonia, proving the precipitate to have been carbonate of lime.

The same general conclusions, then, with regard to the nature of the ingredients, are to be drawn from the preceding results as from the application of the same tests to the Dunblane water. They suggest of course a similar mode of analysis. 1 preferred the second of the methods above described, as being the most simple and easy of execution.

An English pint of the water was submitted to evaporation. Before the matter became dry, numerous cubical crystals were formed, indicating the presence of muriate of soda; when dry, the solid matter entered readily into fusion with effervescence, denoting the predominance of muriate of lime. The dry matter was highly deliquescent. After exposure to a heat inferior rather to redness, it weighed while warm 35 grains.

This dry matter was redissolved in about ten times its weight of distilled water. A small portion remained undissolved, which, being washed and dried, weighed 12 grain. A little diluted muriatic acid dropt upon this excited slight effervescence; but the greater part remained undissolved, and weighed, after washing and exsiccation, 0.9 grain. It was sulphate of lime. A very thin crust adhered to the sides of the glass globe in which the last stage of the evaporation had been performed. This was dissolved with effervescence by diluted muriatic acid, and the solution became quite turbid on adding oxalate of ammonia. The quantity of carbonate of lime thus indicated, adding the portion abstracted, as above, from the sulphate, cannot be estimated at more than 0.5 grain. These results were confirmed by precipitation from another portion of the water by muriate of barytes, the proportions indicated being nearly the

same.

The liquor poured off from the insoluble residue being diluted with distilled water, oxalate of ammonia was added to it as long as any turbid appearance was produced; and after the subsidence of the precipitate the liquor was boiled a little, to render the decomposition and precipitation complete. The clear liquor was then evaporated to dryness, and the dry mass was exposed to heat, to volatilize the muriate of ammonia, the product of the action of the oxalate of ammonia on the muriate of lime; the heat being continued as long

as any vapours exhaled, and at the end being raised to redness. The muriate of soda thus obtained weighed 134 grains. By solution and crystallization it was obtained in cubes.

The precipitate of oxalate of lime having been thoroughly washed, was exposed in a sand-bath to a heat short of redness, until it had ceased to exhale any vapours, and appeared perfectly dry; it weighed 23.8 grains. The portion of muriate of lime equivalent to any quantity of oxalate of lime cannot, as has been already remarked, be exactly assigned, from the difficulty of bringing the oxalate to one uniform state of dryness. But, according to the most accurate analyses, 23.8 grains of dry oxalate are equivalent to 20 grains of dry muriate. To avoid any error, however, the oxalate was converted into carbonate of lime by calcination; and this, decomposed by muriatic acid, afforded 19-5 grains of dry muriate of lime.

The proportions, then, of the saline ingredients in an English pint of the Pitcaithly water are, according to this analysis,

To which are to be added of aerial ingredients,

Atmospheric air.

Carbonic acid gas..

It also gives slight indications of the presence of iron; but as far as can be judged from the shade of colour produced by tincture of galls, the quantity is much smaller than in the Dunblane water. It does not admit, therefore, of being determined with much accuracy by actual experiment.

After I had completed the preceding analysis, a view occurred to me with regard to the composition of these waters, different from that which has been stated above; and which, if just, may lead to conclusions of some interest with regard to the constitution of mineral waters of the saline class. This I have lastly to illustrate.

(To be continued.)

ARTICLE III.

Some Observations on the Analysis of Organic Substances. By Dr. Prout.

BERZELIUS has lately extended the doctrine of definite proportions to the principles of organic nature, and has very satisfactorily

shown that it holds equally good with respect to them, with some slight modifications only, as with inorganic compounds.* His admirable paper on this subject has thrown a new light on the constitution of natural objects, and at the same time opened a field of investigation no less difficult than interesting. My object at present is chiefly to point out the important assistance which may be derived in similar researches from the use of the invaluable scale of chemical equivalents contrived by Dr. Wollaston; a fact well known to its distinguished author, and many others; but which, perhaps, is not so generally so as it ought to be. On the supposition that this instrument be correct, or nearly so, which no one can doubt, and that organic substances be really formed on the principles of definite proportions, we are enabled by its means to approximate in most instances, with almost absolute certainty, to the number of atoms of each element entering into the composition of a ternary or quaternary compound. The data requisite for this purpose are, 1. The knowledge of the proportions of at least two of the elements entering into an organic compound; and, 2. The knowledge of the weight of its atom, or some multiple of it. Of these two, the first is by far the most important; the second is not absolutely necessary.

To render this scale adapted for our purpose, it is only necessary to extend it a little, which may be conveniently done by pasting two slips of drawing paper on its edges, which must be of such a breadth as just to lap over and cover the margins containing the names of the chemical substances, and to coincide with the graduated edges of the slide. On these slips of paper are then to be marked the multiples of an atom of oxygen, hydrogen, and carbon, from one to ten; and of ażote, from one to four or five, or more. Thus prepared, it will be fit for our use; and to those who are unacquainted with the principles of the instrument, the following examples will show the mode of applying it: to others these examples will be probably unnecessary.

Example 1.-Suppose we had found the weight of a particle of a ternary compound to be 46.5, oxygen being 10, and that 46.5 parts of it contained 15:15 carbon, 134 hydrogen, and consequently 30-01 oxygen. To find the number of atoms of each of these elements, we have only to place 10 on the slide opposite oxygen, and then opposite each of the numbers respectively we have the number of atoms of each element required. Thus opposite 15-15 carbon, we have 2 carbon; opposite 1:34 hydrogen, 1 hydrogen; and opposite 30.01 oxygen, 3 oxygen. Such a compound, then, will consist of three atoms oxygen, two atoms carbon, and one atom hydrogen.

Again: supposing we were ignorant of the weight of an atom of this ternary compound, but had found that 100 parts of it contained 32.4 carbon, 28 hydrogen, and consequently 64.8 oxygen; to find the number of atoms of each element in this case we have only to

* See Ammals of Philosophy, vol. iv. p. 323, et sequent.

move the slide till the numbers representing the quantities of each element coincide with some multiple of these elements marked on the scale; and these multiples, or some submultiple of them, will represent the number of atoms required. Thus we find when 32.4 carbon stands opposite two or four atoms of carbon, 2.8 hydrogen will coincide with one or two atoms of hydrogen, and 64.3 oxygen with three or six atoms of oxygen. Of course we adopt the lesser numbers, which are the same as those obtained before.

Example 2.-Suppose we had found the weight of an atom of a quaternary principle to be 97.82, and that 97.82 parts of it contained 37 65 carbon, 17.52 azote, and consequently 42.65 oxygen and hydrogen: to find the number of atoms of each, we place, as before, 10 on the slide opposite oxygen: then opposite 37.65 will be found 5 carbon; opposite 17 52, 1 azote; opposite 40, 4 oxygen; and opposite 265, 2 hydrogen; the number of atoms required.

*

Or supposing that we had not been able to ascertain the weight of a particle of the compound in question, but had found that 100 parts of it contained 38.5 carbon, 17.9 azote, and consequently 43.6 oxygen and hydrogen: to find the number of atoms of each, we proceed just as before, and still find that 38.5 carbon will stand opposite five or ten atoms of carbon, when 17.9 azote coincide with one or two atoms of azote; † and that 40·9 oxygen will be opposite four or eight oxygen; and 2-7 hydrogen, opposite two or four hydrogen; which agree with the former results.

These examples are doubtless more than sufficient to show how this admirable instrument may be made to facilitate and verify analyses, on the practical part of which some observations now remain to be made.

1. The depriving organic substances of water without decomposing them has always constituted a great source of difficulty in the prosecution of this department of chemistry. The method adopted by Berzelius, and which is founded on the happy applica tion of a well-known principle by Mr. Leslie, is certainly one of the best that has been proposed. This consists in exposing the substance

* These two numbers make up 42.65, the quantity of oxygen and hydrogen present. As no solid substance, probably, will be found to contain more than six or even four atoms of hydrogen, it will perhaps be sufficient in practice to divide as often as possible the quantity of oxygen and hydrogen by the weight of a par ticle of oxygen, and to consider the quotient as representing the number of par ticles of oxygen, and the remainder as hydrogen. Thus in the present instance 42.65 4, with a remainder of 2:65 for hydrogen, and 10 × 4 40, the quan10 tity of oxygen. To prevent ambiguity, however, it will be better to have recourse to experiment, which without any great nicety will enable one to decide between one and eight atoms of hydrogen, as in the above instance between 2.65 hydrogen and 12.65 hydrogen.

+ It is extremely probable that azote never enters into a compound more than in one, or certainly not more than in two, proportions. The knowledge of this will facilitate the process, as the quantity of azote found may be at once placed opposite one azote,