Page images
PDF
EPUB

What is the medium of communication between the spleen and stomach, is as yet unknown. But if the main fact be, well established, we doubt not that the route will be detected by the industry of future anatomists.

111 'On the Composition of the compound Sulphuret from Huet, Boys, und an Account of its Crysials. By James Smithson, Esq. F.R.S.

IV. On Oxalic Acid. By Thomas Thomson, M.D. F.R.S Ed. Communicated by Charles Hatchett, Esq. F.R.S.

It is the object of this elaborate essay, not to give a complete history of the oxalic acid, but to state the result of a set of experiments undertaken with a view of ascertaining some particulars concerning it which are of importanee.

1. Water of Crystallization. --Crystals of oxalic acid cautiously heated on a sand bath, fall into powder, and lose about one-third of their weight. But as the acid is itself volatile, the whole loss probably is not waler. To determine the proportion of water, therefore, he foroved an oxalate of lime containing a known quanlity of crystallized acid (58.3) grains. The oxalate dried on a sand' weighed 72 grains, which exposed to an intense heat left 27 grains of pure lime. The oxalate must have contained then 45 grains of real acid, which gives 13.3 grains of of water. In 100 parts of acid, therefore there will be real acid 77. water 23.

2. Alkaline and earthy oxalates. The most important of these compounds is the oxalate of time, of which we have given the proportion of the elements. It was formed by precipitating muriale of lime by oxalic acid. It is necessary when the liquor ceases to precipitate, tu saturate the muriatic acid, evolved with ammonia ; thus more oxalate is obtained, and by adding fresh oxalic acid still more, by carefully alternating these processes all the lime may be precipitated. Bergmann by trusting to a single precipitation was deceived, and has given erroneous proportions; to avoid all chance of error, Dr. Thomson precipitated liine water with oxalic acid, and obtained exactly the same result, viz. in 100 parts of oxalete 62,5 acid, and 57.3 base.

The doctor proceeds to enumerate the properties of the other earthy and alkaline oxalates, and the proportions of their elements. We must content ourselves with giving his results which are contained in the following table.

[merged small][merged small][merged small][ocr errors][merged small][merged small][merged small]

To form these salts Dr. F. directly combined solutions of the acid with the salts and earths. But be formed another oxalate of strontian by mixing a known weight of oxalate of ammonia with a solution of muriate of strontian. In the salts formed 100 parts of acid saturated only 75.7 of base. There are then two oxalates of strontian ; and it is remark. able that that in the table contains just double the proportion of base contained in the last,

3. Decomposition of the Oralates ---As a part of the oxalic acid is sublimed by heat, a complete decomposition cannot be effected by exposing the acid alone to the action of fire, But when an alkaline or earthy oxalate is heated, the acid remains fixed till it undergoes a complele decomposition. The new substances are the same, whatever are the oxalates employed. The products are, water, carbonic acid, carbonic oxide, carbureted hydrogen, and charcoal. Our limits will not permit us to enter into the detail of pro. cesses by which Dr. Thompson had endeavoured to determine the exact proportion of these substances. We must con, tent ourselves with noticing the conclusions. The statement is as follows: .. When the different elements are collected under their proper beads, we obtain. 1. Oxygen in carbonic acid - ; - 42.86

- inflammable air, - - 11.96
- water - - - - - - 9.87

64.69
Carbon in carbonic acid . - - 16.67.
- inflammable air -. '- 10.43
- - charcoal . . - 4.68

. *31.78 . Ilydrogen in inflammable air 1.89

non - Water - - - - - 1.04

Hence oxalic acid is composed of oxygen 64. 69, of carbon 31, 78, of hydrogen 3.53.” Total 100.00.

1. Composition of oxalic acid. It has been ascertained,? says Dr. Thomson, by numerous and decisive experiments, that elementary bodies always enter into combinations in determinate proportions, which may be represented by nombers, For example, the numbers which correspond to the four elements, oxygene, azote, carbon and hydrogen, are the following, Oxygen, 6; Azote, 5 ; Carbon, 4.5; Hydrogen 1. Now in all compounds consisting of these ingredients, the proportion of the different constituents may be always represented by these numbers or by mulriples of them, . From the knowledge of this curious law, it is dif, ficult to avoid concluding that each of these elements consists of atoms of determinate weight, which combine according to certain fixed proportions, and that the numbers above given, represent the relative weights of these atoms respectively. Thus an atom of oxygen weighs 6, an atom of hydrogen, 1, &c. Water is composed of one atom of oxyger and one atom of hydrogen ; carbonic acid of twa, atoms of oxygen and one of carbonic,

This is the theory of Mr. Dalton, concerning which we expect more copious details in the second part of his new system of chemistry. It is a consequence of this law that the elements of bodies, as in the salis, the acids, and bases, combine particle with particle, or a certain delerminate number of particles of the one with a particle of the other. Dr. T. has shown in the case of the oxalic acid (the number of which is calculated to be 89.5),that if an integrant particle of this acid be supposed to be made up of 4 atoms of oxy. gen, 3 atoms of carbon, and 2 atoms of hydrogen, 110 parts of oxalic acid would in this case be composed of 61 parts of oxygen, 34 parts of carbon and 3 of bydrogen. These numbers approach so nearly to the result of the actual analysis that they give to the reasoning employed at least a very high degree of probability.As the lumbers themselves are not as yet ascertained with rigid accuracy greater precision cannot be expected ; but it is obvious that this theory promises to introduce a degree of inathematical precision, and to throw an unexpected light on the obscurest parts of chemistry.

5. Composition of Sugar, and Formation of Oxalic Acid.

•Sugar,'the doctor observes is probably a more compound body than oxalic acid, because nitric acid resolves it into a variety of more compounds; one of which is uxalic acid.

In the formation of the acid, by the action of nitric acid, 100 grains of sugar yield

grains. 1. Oxalic acid crystals 53 grains, or real acid

45 2. Carbonic acid 100 cubic inches, equivalent to 46:5 Also: 1. Azotic gas 35 cubic inches, equivalent to

10.62 . 2. Nitrious gas 32 cubic inches, equivalent to

10.85 The carbon, in the two first quantities are respectively 14. 40 and 13.02 grains, making a total of 27.42 grains in 100 of sugar. If the whole of the oxygen in the carbonic acid came from the nitric acid (which is most probable) then that irti the oxalic was a part of the sugar which is (from the preceding analysis) 28.8, with which its carbon (27.5) and hydrogen (1.8) make a total of 58.1. But 100 grains of sugar have totally disappeared. It must be supposed then

that the remainder of 41.9 grains have been converted into 1 water, which are composed of oxygen 35.9 and hydrogen

6 grains. These quantities added to the preceding pro. ducts give the following figures (in grains) for the coolposition of sugar, viz. oxygen 04.7, carbon 27.5, hydrogen 7.8. Lavoisier used a different method of computation, but obtained a result very nearly coinciding with the above. His numbers are, oxygen 64. carbon 28. hydrogen 8.

V. On super-acid and sub-acid Salts. By William Hyde Wollaston, `01. D. Sec. R. S.--Previous to the publication of Mr. Dalton's theory, Dr. Wollaston had observed, he informs, us, that in various instances of super-acid and subacid salts, the quantity of acid in the former was a simple multiple of the quantity in the latter. This is a particular instance of the general observation of Mr. Dalton' that in all cases the simple elements of bodies, are disposed to unite atom to atum singly, or, if either is in excess, it exceeds by a ratio to be expressed by some simple 'multiple of the number of its atoms.' .

Dr. Wollaston has illustrated this truth by some easy experiments, conducted with that peculiar precision, elegance and simplicity which so much distioguish whatever proceeds from him. He has shown that the carbonates of potash and soda contain just twice ihe quantity of carbonic acid that enters into the sub-carbonates. The super-sulphate of potash, and super-oxalate of potash contain just twice as much acid as the neutral sulphate and oxalate do. If the super-oxalate be decomposed by the nitric or muriatic acid,

these latter take half the alkali : consequently the salt obtained from such a solution by crystallization has four times as much acid as the neutral compound, or is a quadrosalate of potash. To prove this, expose tbirty grains of this salt (previously purified by cristallization) to redness ; the alkali obtained from it will exactly neutralize the redundant acid contained in ten grains of the same salt. ... The quantity of unburned salt contains alkali for one part out of four of the acid present, and it requires the alkali of three equal quantities of the same salt to salurate the three remaining parts of acid."

Thirty grains of oxalic acid were found to neutralize infortyeight of carbonale (qu. sub-carbonate?) of potash. To this sq. lution were added sixty grains more of oxalic acid. By crystallization two salts were obtained, the binoralate, or common salt of sorrel, and the quadrocolates. No salt can be formed containing a quantity of acid intermediates between the doua ble and quadruple quantity.

Dr. Wollastun concludes bis paper with a short speculation on the geometrical position, which the particles of a body must occupy, in order to form a permanent union with another of a different species, to which it is attracted. But he admits that the hypothesis is altogether conjectural, and we fear, with him, that it is too much to hope ihat the geo, metrical arrangement of primary particles will ever be perfectly known.

VI. On the Inconvertibility of Bark into Alburnum. By Thomas Andrew Knight, Esq. F. R. S. In a Letter to Sir Joseph Bunks, K. B. F. R. $-We believe that few who are acquainted with the mode of nourishment and growth of animal bodies, and who are also sensi. ble that in these processes there is an analogy preserved though all living and organised being, require to have it demonstrated that the bark of trees is not convertible into their wood. No physiologists now suppose that perios. teum is converted into bone; but we koow that ossification is the effect of a secretion froni appropriate vessels. But as eminent naturalists have believed in the transın utation of baik ioto alburnum, Mr, Knight, we think, bas not done amiss to attempt experimentally to prove the converse.

He look branches of crab and an apple tree of equal sizes, and firmly applied the bark of the une lo the

stem of the other; covered the parts with bandages, and : excluded ibe air by a composition of wax and turpentine, and

« PreviousContinue »