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It is a bad omen to stumble at the threshold, but we cannot help it: Mr. Gray thus defines chemistry :-" The alterations and appearances that take place in the admixture of bodies, and the action of heat and cold upon them, are the proper objects of chemistry; which also endeavours to explain the production of similar phenomena when they arise from other causes.”

Now unless cold be a positive power, which we suppose Mr. Gray will not contend that it is, the effects of cold are referrible to alterations of temperature, and consequently to the subject of heat itself; what the similar phenomena are which arise from other causes besides chemical action, we are quite at a loss to conjecture.

After giving the theory of combustion, which we must pass over without remark, Mr. Gray proceeds (p. 189) to the consideration of the

"Compound Combustibles.-The more simple substances being thus gone through, it remains only to treat of those compound combustibles, which are, generally speaking, produced in organic bodies, or from bodies having that origin. Some of them, indeed, are so loaded with water or other incombustible matter, as vinegar or oyster shells, that they appear, to a common observer, to be themselves incombustible; but when the water or other extraneous matter is separated, this appearance vanishes. In point of chemical composition, they are, generally speaking, compounds of carbon, hydrogen, and oxygen, to which are sometimes added nitrogen and other ingredients: hence they are distinguished from the combustibles of the former series, in always forming both carbonic acid and water by their union with more oxygen."

Some further observations succeed the above, and we then arrive at the "Pharmaceutical Division of Combustibles; " and Mr. G. informs us, that the divisions which the "pure chemists" have formed, are not followed in his work. "Spirit of wine and vinegar, being of continual use in chemistry, as agents in the preparation and examination of bodies, are first noticed; and the remainder of the combustible bodies are arranged according to their taste, as being the quality that is usually first attended to in examining them, and which has also a considerable connexion with their medical virtues. For the sake of elementary brevity, scarcely any other of these articles but those enumerated in the Materia Medica of the London College of Physicians are noticed. The arrangement of these combustible drugs is as follows:

1. Earthy and absorbent bodies.

2. Farinaceous, mucilaginous, gelatinous, gummy, and emollient bodies.

3. Bitter bodies.

4. Austere and acerb bodies.

5. Acid bodies.

6. Aromatic bodies.

7. Fat and oily bodies.

8. Sweet bodies.

9. Acrid bodies.

It will, perhaps, be scarcely credited when we state, that the first "combustible drug," which its "taste" has assigned a place among the earthy and absorbent bodies, is incombustible and tasteless. When treating of "the earthy and absorbent bodies," Mr. Gray says, "only one compound combustible substance of this kind is now quoted in the London Pharmacopœia, namely, testæ.

"Testa.-Oyster shells consist of carbonate of lime deposited in a tissue of gelatinous matter, which latter is very small in quantity; hence they are used only as antacids. On calcination, the gelatinous matter is burned, the carbonic is driven off, and a pure lime remains." Now as chalk is quoted in the London Pharmacopoeia, as well as oyster shells, the reader will wonder with us how it happened not to be arranged with the earthy and absorbent bodies; it is true that it has no taste, and is not combustible; but it is at least as sapid and as combustible as oyster shells; the reason we suppose to be, that as shell contains a small quantity of gelatinous matter which is combustible, but to which it owes none of its absorbent powers, it is ranked among the compound combustibles. We think we need scarcely ask, whether any arrangement can be essentially good which separates two varieties of carbonate of lime, because one contains an admixture of gelatinous matter.

The substances brought together under the name of farinaceous bodies, are as dissimilar as bodies can be. Among them are gum arabic, wax, horns, henbane leaves, and eggs.

Arrangement, however, is a matter of secondary importance, provided the substances when met with are accurately described; but there are many instances of inaccuracy in Mr. Gray's work, some of which, taken at random, we shall point out, premising, however, that we did not expect to find phosphorus and sulphur among the "Metallic Elements" (p. 84).

The first error which we shall notice occurs at p. 95: "Thus oil of vitriol, being composed of three charges of oxygen, united to one of sulphur and ten of water, which last is itself supposed to be composed of a single charge each of oxygen and hydrogen, the compound is expressed thus: S+000+ 10 (H + 0); or more concisely, thus, SO3 + 10 (H O); or still more concisely, thus, S3 + 10 H1." This passage we have quoted somewhat at length, because it proves incontestably, that Mr. Gray is ignorant of the composition of sulphuric acid; for he has once in words, and three times by symbols, misstated its nature. It may, perhaps, be requisite to observe, that by the word charge Mr. Gray means what other chemists term atom, proportional or prime; but oil of vitriol instead of containing ten charges of water, contains only one, as may be seen in any

modern work of the “ pure chemists." It might be supposed that the word ten, was accidentally substituted for one, of water; but the symbols agreeing with the former, we must admit what we find so often repeated, to express the state of the author's knowledge on the subject, and it is astonishing that it should be so erroneous.

In p. 177, Mr. Gray states, that from "the quantity of ammonia required for saturating acids, it may in consequence of this law be inferred that ammonia contains about 46 per cent. of oxygen; and its change into azotic gas and hy drogen gas, by being passed through a red-hot tube, shows that this is united with 36 of nitricum and 18 of hydrogen; so that the composition of ammonia is 6 H + N + O." If there be any thing in chemical science which appears to be settled, it is, that ammonia contains no oxygen; and the view which Mr. Gray has given of its composition is calculated to puzzle much more than to inform. If the student after reading this passage were to look into the chemical works of Thomson, Henry, or Brande, he would find no mention either of oxygen or nitricum existing in ammonia. These speculations of Berzelius respecting the compound nature of azote, should have found no place in an elementary work.

The statements of the nature and atomic constitution of the various salts are such as will give the pupil no idea of their composition; thus in p. 204, we are told that "acetic acid, boiled on about one-quarter of its weight of litharge to threequarters its bulk, then set by to settle and poured off clear, is the liquor plumbi acetatis of the Pharmacopoeia, a dram of which added to a pint of water, and a dram measure of proof spirit, forms the well-known Goulard's lotion. These are solutions of a salt which may be crystallized in plates, and is a subtritacetate of lead, or acet. ac. + 3 ox. lead."

The fact is, that this solution is a subbinacetate of lead, but if it were what Mr. Gray represents it to be, what idea of the proportions of its constituents can the pupil acquire, without knowing the weight of the atoms of acetic acid and oxide of lead? The composition of 100 parts ought to have been stated in the usual way; added to this when treating of the nomenclature of salts in p. 81, no rules are given for describing those which contain an excess of base. On the same ground we object to the following statement: "Moist iodine added to phosphorus yields a sour colourless gas, which is rapidly absorbed by water, and must be collected in a quicksilver apparatus; a gallon of this gas weighs about 311 grains. Here the changes are either IP into I2+ P', or I+P+ H' into IHP'; and the new acid is called the iodic or hydroiodic." The pupil would naturally suppose, that Mr. Gray considers the iodic and hydroidic acids (properly hydriodic) as similar; but he ought to have known, that iodic acid consists of oxygen and

iodine, and the hydriodic acid of hydrogen and iodine; it is the latter only which is formed, excepting a quantity of phosphorous acid, of which no notice is taken, nor is the decomposition of he water even hinted at, although the formation of the hydriodic acid depends upon it (p. 166).

The directions for detecting the presence of arsenious acid (p. 151) are thus given in eight lines:-" If a person is suspected to be poisoned with arsenic, the antidote that is most readily obtained is a solution of soap; and the contents of the stomach may, to obtain satisfaction, be dissolved in boiling distilled water, the solution strained, and then, if any white arsenic has been taken up, on the surface being touched with a stick of lunar caustic, a sulphur-yellow precipitate will fall down immediately from the place touched." These directions are incorrect, and totally inefficient; for it is necessary to make use of solution of an alkali, either carbonate of potash as proposed by Mr. Hume, or ammonia as preferred by Dr. Marcet, Besides this omission, Mr. G. has not stated one word of the ambiguity which may arise from the presence of a phosphoric salt, nor does he give any directions for procuring the confirmatory evidence which may be obtained by the use of sulphuretted hydrogen, sulphate of copper, or from the alliaceous smell; nor is the direct evidence afforded by metallization in any way alluded to.

We cannot help noticing the contemptuous and unwarrantable language which Mr. Gray employs when speaking of Lavoisier, a philosopher to whom every one, but Mr. Gray, knows that science is deeply indebted, and whose misfortunes entitle his memory to respect. "Lavoisier reversed the analogy, and instead of continuing to identify the metallic oxides with the earths, compared the earths to the metallic oxides; and, being a Frenchman, he of course claimed this mere shifting of the terms of the analogy, as a great discovery."

With one more quotation, we shall conclude our notice of the Elements of Pharmacy. In page 88, some of the properties of azote, chlorine, and iodine, are mentioned, and then come the following observations: "All of these are esteemed by Sir H. Davy, Brande, and the chemists of that school, as simple bodies in the present state of our knowledge, but Berzelius and the rationalists consider them as oxides; the supposed bases of the two first being called by him nitricum, muriaticum, and that of the third may be distinguished by the name of iodium." Thus we have an author who has four times misstated the composition of sulphuric acid, venturing to divide chemists into the two classes of the rationalists and irrationalists, and placing among the latter the inventor of the safety lamp.-Edit.

ARTICLE XV.

SCIENTIFIC INTELLIGENCE, AND NOTICES OF SUBJECTS CONNECTED WITH SCIENCE.

I. On the Ignition of Platina, &c. by Hydrogen Gas.

I have, says Prof. Dæbereiner, already proved that the protoxide of platinum obtained by Edmund Davy's method, has the property of causing alcohol, placed in contact with it, to attract oxygen gas, and to become converted into acetic acid and water; and that this property is likewise possessed by the oxidized sulphuret of platinum, prepared by treating a solution of that metal with sulphureted hydrogen, and exposing in a dry state the sulphuret formed by that means, to the action of atmospheric air for some weeks. In this very remarkable process, 1 atom (= 46) of alcohol combines with 4 atoms (= 4 × 8 = 32) of oxygen, and forms with it 1 atom (= 51) of acetic acid, and 3 atoms (= 3 x 9 = 27) of water; that is so say, equal volumes of the vapour of alcohol and oxygen gas, become equal volumes of acetic acid and aqueous vapour; for 1 atom of water is requisite to the isolated existence of acetic acid. The respective proportions in which acetic acid and water appear in this case, are exactly the same as those which they bear to each other in crystallized sugar of lead, and also in the subacetate of copper; the quantity of water in acetate of soda is exactly double that which is contained in each of the former acetates.

After having finished my experiments on this process of the formation of acetic acid, I took the opportunity of ascertaining the relations of the two above-named preparations of platinum to different elastic fluids. The results of the experiments instituted for that purpose are interesting; for I found,

1. That neither oxygen nor carbonic acid gas was absorbed by the protoxide, or by the oxidized sulphuret of platinum; but that those substances absorbed every inflammable gas.

2. That 100 grains of protoxide of platinum absorb from 15 to 20 cubic inches of hydrogen gas, during which absorption so much caloric is evolved, that the protoxide becomes ignited, and the hydrogen burns with detonation, if it had been previously mixed with oxygen or with atmospheric air.

The preparation of platinum, charged with hydrogen, has the property of greedily attracting as much oxygen gas as is requisite for the saturation of the hydrogen it contains. If atmospheric air, there. fore, be suffered to enter the tube containing it, it instantly deprives it of its oxygen, and even forms ammonia with a portion of the residual nitrogen, if there be not sufficient oxygen present for its saturation. By this agency the oxide of platinum is reduced, and thereby loses its remarkable property of disposing alcohol to become acetic acid, and also that of condensing hydrogen gas; but, what is very remarkable, it retains the property of determining the latter substance to the state in which it combines with oxygen gas, and becomes water; and so much heat is evolved during this combination, that if the hydrogen gas be mixed with pure oxygen, and the volume of the

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