Part 1 — APPENDIX. (continued 2)

The facts above stated appear to me to place the constitution of alum in a clearer point of view than any other I have seen. They make no difference in the weights of the several elements in 100 grains of the salt, from what we have given in Vol. 1; only the weight of the atom of alumine is here taken to be 20 instead of 15, and we have 3 atoms of it in 1 of alum, instead of 4, as in the former account.

ON THE PRINCIPLES OF THE ATOMIC SYSTEM OF CHEMISTRY.

It is generally allowed that the great objects of the atomic system are, 1st to determine the relative weights of the simple elements; and 2d to determine the number, and consequently the weight, of simple elements that enter into combination to form compound elements. The greatest desideratum at the present time is the exact relative weight of the element hydrogen. The small weight of 100 cubic inches of hydrogen gas, the important modifications of that weight by even very minute quantities of common air and aqueous vapour, and the difficulties in ascertaining the proportions of air and vapour in regard to hydrogen, are circumstances sufficient to make one distrust results obtained by the most expert and scientific operator. The specific gravity of hydrogen gas was formerly estimated at ⅒ that of common air; it descended to ¹/₁₂.₅, which is the ratio we adopted in the Table at the end of Vol. 1. it is now commonly taken to be ¹/₁₄.₅, and whether it may not in the sequel be found to be ¹/₁₆.₅ is more than any one at present, I believe, has sufficient data to determine. The other factitious gases have mostly undergone some material alterations in their specific gravities in the last twenty years, several of which I have no doubt are improvements; but when we see these specific gravities extended to the 3rd, 4th, and 5th places of decimals, it appears to me to require a credit far greater than any one of us is entitled to. In the mean time, it may be thought a fortunate circumstance, that the weight of common air has undergone no change for the last thirty or forty years; 100 cubic inches bring estimated to weigh 30.5 grains at the temperature of 60°, and pressure of 30 inches of mercury: (whether this is exclusive of the moisture I do not recollect.) It is also a fortunate circumstance, (provided it be correct) that this weight is nearly free from decimal figures. I may be allowed to add, that according to my experience, the weight of 100 cubic inches of air is more nearly 31 grains than 30.5. I apprehend these observations are sufficient to shew that something more remains to be done before we obtain a tolerably correct table of the specific gravities of gases; the importance of this object can not be too highly estimated.

The combinations of gases in equal volumes, and in multiple volumes, is naturally connected with this subject. The cases of this kind, or at least approximations to them, frequently occur; but no principle has yet been suggested to account for the phenomena; till that is done I think we ought to investigate the facts with great care, and not suffer ourselves to be led to adopt these analogies till some reason can be discovered for them.

The 2d object of the atomic theory, namely that of investigating the number of atoms in the respective compounds, appears to me to have been little understood, even by some who have undertaken to expound the principles of the theory.

When two bodies, A and B, combine in multiple proportions; for instance, 10 parts of A combine with 7 of B, to form one compound, and with 14 to form another, we are directed by some authors to take the smallest combining proportion of one body as representative of the elementary particle or atom of that body. Now it must be obvious to any one of common reflection, that such a rule will be more frequently wrong than right. For, by the above rule, we must consider the first of the combinations as containing 1 atom of B, and the second as containing 2 atoms of B, with 1 atom or more of A; whereas it is equally probable by the same rule, that the compounds may be 2 atoms of A to 1 of B, and 1 atom of A to 1 of B respectively; for, the proportions being 10 A to 7 B, (or, which is the same ratio, 20 A to 14 B,) and 10 A to 14 B; it is clear by the rule, that when the numbers are thus stated, we must consider the former combination as composed of 2 atoms of A, and the latter of 1 atom of A, united to 1 or more of B. Thus there would be an equal chance for right or wrong. But it is possible that 10 of A, and 7 of B, may correspond to 1 atom A, and 2 atoms B; and then 10 of A, and 14 of B, must represent 1 atom A, and 4 atoms B. Thus it appears the rule will be more frequently wrong than right.

It is necessary not only to consider the combinations of A with B, but also those of A with C, D, E, &c.; as well as those of B with C, D, &c., before we can have good reason to be satisfied with our determinations as to the number of atoms which enter into the various compounds. Elements formed of azote and oxygen appear to contain portions of oxygen, as the numbers 1, 2, 3, 4, 5, successively, so as to make it highly improbable that the combinations can be effected in any other than one of two ways. But in deciding which of those two we ought to adopt, we have to examine not only the compositions and decompositions of the several compounds, of these two elements, but also compounds which each of them forms with other bodies. I have spent much time and labour upon these compounds, and upon others of the primary elements carbone, hydrogen, oxygen, and azote, which appear to me to be of the greatest importance in the atomic system; but it will be seen that I am not satisfied on this head, either by my own labour or that of others, chiefly through the want of an accurate knowledge of combining proportions.

NEW TABLE OF THE RELATIVE WEIGHTS OF ATOMS.

At the close of the last volume, the weights of several principal chemical elements or atoms were given; but as several additions and alterations have been educed from subsequent experience, it has been judged expedient to present a reformed table of weights.

SIMPLE ELEMENTS.

Weights.

Hydrogen 1

Azote 5±, or 10?

Carbone 5.4

Oxygen 7

Phosphorus 9

Sulphur 13, or 14

Calcium 17?

Sodium 21

Arsenic 21

Molybdenum 21, or 42?

Cerium 22?

Iron 25

Manganese 25

Nickel 26

Zinc 29

Tellurium 29, or 58?

Chromium 32

Potassium 35

Cobalt 37

Strontium 39

Antimony 40

Iridium 42

Palladium 50

Uranium 50, or 100?

Tin 52

Copper 56, or 28?

Rhodium 56

Titanium 59?

Gold 60±

Barium 61

Bismuth 62

Platina 73

Tungsten 84, or 42?

Silver 90

Lead 90

Columbium 107? 121?

Mercury 167, or 84?

SIMPLE OR COMPOUND?

Weights.

Fluoric Acid 10? 15?

Magnesia 17

Alumine 20

Glucine 23? 34?

Lime 24

Oxymuriatic Acid (chlorine) 29, or 30

Muriatic Acid 30, or 31

Gas

Zircone 45

Silex 45?

Yttria 53? 36? 18?

COMPOUND ELEMENTS.

Weights.

Ammonia 6? 12? 13?

Olefiant Gas 6.4? 12.8?

Carburetted Hydrogen 7.4

or Pond Gas

Water 8

Phosphuretted Hydrogen 10

Nitrous Gas 12, or 24?

Carbonic Oxide 12.4

Sulphuretted Hydrogen 15

Deutoxide of Hydrogen 15

Nitrous Oxide 17

Nitrous Acid 19, or 38?

Carbonic Acid 19.4

Sulphurous Oxide 21

Phosphoric Acid 23

Sulphurous Acid 28

Protoxide of Arsenic 28

Soda 28

Hydrate of Lime 32

Protoxide of Iron 32

Protoxide of Manganese 32

Protoxide of Nickel 33

Sulphuric Acid 35

Sulphuret of Arsenic (native) 35

Hydrate of Soda 36

Oxide of Zinc 36

Carbonate of Magnesia 36.4

Protosulphuret of Iron 39

Deutoxide of Manganese 39

Oxide of Chromium 39

Muriate of Magnesia 39

Protosulphuret of Nickel 40

Protosulphuret of Lime 41

Carbonate of Lime 43.4

Protoxide of Cobalt 44

Strontites 46

Muriate of Lime 46

Chromic Acid 46

Protoxide of Antimony 47

Carbonate of Soda 47.4

Hydrate of Potash 50

Muriate of Soda 50

Sulphate of Magnesia 52

Sulphuret of Antimony 54

Sulphate of Alumine (simple) 55

Oxide of Palladium 57

Sulphate of Lime 59

Protoxide of Tin 59

Carbonate of Potash 61.4

Hydrosulphuret of Antimony 62

Nitrate of Magnesia 62

Sulphate of Soda 63

Protoxide of Copper 63

Muriate of Potash 64

Deutoxide of Tin 66

Protosulphuret of Tin 66

Oxide of Gold 67

Barytes 68

Muriate of Lime 69

Oxide of Bismuth 69

Deutoxide of Copper 70

Nitrate of Soda 73

Sulphuret of Gold 74

Protosulphuret of Bismuth 76

Sulphate of Potash 77

Oxide of Platina 80?

Nitrate of Potash 87

Carbonate of Barytes 87

Muriate of Barytes 90

Oxide of Silver 97

Protoxide of Lead 97

Minium 98

Sulphate of Barytes 103

Deutoxide of Lead 104

Protosulphurets of Lead and Silver 104

Nitrate of Barytes 113

Protoxide of Mercury 174?

Deutoxide of Mercury 181?

Protosulphuret of Mercury 181

Alum 277