THE COMBINING WEIGHTS, VOLUMES, AND SPECIFIC GRAVITIES OF ELEMENTS AND COMPOUNDS.
Under the title of "Figures Worth Studying," Mr. William Farmer, of New York, read a paper before a recent meeting of the Society of Gas Lighting, from which the American Gas Light Journal gives the following:
I have prepared the following table, which contains some of the elements and compounds, with their combining weights, volumes, and specific gravities. When the combining weight of any of these elements and compounds is taken in pounds, then the gas or vapor therefrom will always occupy about 377.07 cubic feet of space, at 60° Fahr. and 30 inches barometer. If we divide this constant 377.07 by the combining weight of any of the substances, then the quotient will be the number of cubic feet per pound of the same. If we divide the combining weight of any of the substances given in the table by 2, then the quotient will give the density of the same, as compared with hydrogen. If we divide the combining weight of any of the substances by the constant 28.87, then the quotient will be the specific gravity of the gas or vapor therefrom, as compared with air. All the calculations are based on the atomic weights which are now generally adopted by the majority of chemists.
| Combining Weight. | Cub. Ft. per Pound. | Cub. Ft. per Combining Weight. | Specific Gravity, Air = 1. | |
|---|---|---|---|---|
| Hydrogen (H2) | 2.00 | 188.53 | 377.07 | 0.0692 |
| Carbon vapour (C2) | 23.94 | 15.75 | 377.07 | 0.8292 |
| Nitrogen (N2) | 28.06 | 13.43 | 377.07 | 0.9719 |
| Oxygen (O2) | 31.92 | 11.81 | 377.07 | 1.1056 |
| Chlorine (Cl2) | 71.00 | 5.31 | 377.07 | 2.4593 |
| Bromine (Br2) | 160.00 | 2.35 | 377.07 | 5.5420 |
| Flourine (F2) | 38.00 | 9.92 | 377.07 | 1.3162 |
| Iodine (I2) | 253.20 | 1.48 | 377.07 | 8.7703 |
| Sulphur (S2) | 63.96 | 5.89 | 377.07 | 2.2154 |
| Phosphorus (P4) | 123.84 | 3.04 | 377.07 | 4.2895 |
| Carbonic oxide (CO) | 27.03 | 13.50 | 377.07 | 0.9674 |
| Carbonic acid (CO2) | 48.89 | 8.59 | 377.07 | 1.5202 |
| Water vapour (H2O) | 17.06 | 20.99 | 377.07 | 0.6221 |
| Hydrogen sulphide (H2S) | 33.08 | 11.09 | 377.07 | 1.1770 |
| Ammonia (H2N) | 17.03 | 22.14 | 377.07 | 0.5898 |
| Sulphurous oxide (SO2) | 63.90 | 5.90 | 377.07 | 2.2133 |
| Sulphuric oxide (SO3) | 79.86 | 4.72 | 377.07 | 2.7662 |
| Cyanogen (C2N2) | 52.00 | 7.25 | 377.07 | 1.8011 |
| Bisulphide of carbon (CS2) | 75.93 | 4.96 | 377.07 | 2.6300 |
| Ethyl alcohol (C2H6O) | 45.90 | 8.21 | 377.07 | 1.5898 |
| Ethyl ether (C4H10O) | 73.84 | 5.10 | 377.07 | 2.5576 |
| Methyl alcohol (CH4O) | 31.93 | 11.81 | 377.07 | 1.1059 |
| Methyl chloride (CH3Cl) | 50.47 | 7.47 | 377.07 | 1.7482 |
| Carbonyl chloride (COCl2) | 98.93 | 3.81 | 377.07 | 3.4267 |
| Phosphine gas (PH3) | 33.96 | 11.10 | 377.07 | 1.1769 |
| Hydrochloric acid (HCl) | 36.50 | 10.33 | 377.07 | 1.2642 |
| Methane (CH4) | 15.98 | 26.61 | 377.07 | 0.5531 |
| Ethane (C2H6) | 29.94 | 12.50 | 377.07 | 1.0370 |
| Propane (C3H8) | 43.91 | 8.58 | 377.07 | 1.5209 |
| Butane (C4H10) | 57.88 | 6.51 | 377.07 | 2.0048 |
| Ethene (C2H4) | 27.94 | 13.49 | 377.07 | 0.9677 |
| Propene (C3H6) | 41.91 | 8.99 | 377.07 | 1.4516 |
| Butene (C4H8) | 55.88 | 6.74 | 377.07 | 1.9355 |
| Ethine (C2H2) | 25.94 | 14.53 | 377.07 | 0.8985 |
| Propine (C3H4) | 39.91 | 9.44 | 377.07 | 1.3824 |
| Butine (C4H6) | 53.88 | 6.98 | 377.07 | 1.8662 |
| Quintone (C5H6) | 65.85 | 5.72 | 377.07 | 2.2809 |
| Benzene (C6H6) | 77.82 | 4.84 | 377.07 | 2.6955 |
| Styrolene (C8H8) | 103.75 | 3.63 | 377.07 | 3.5936 |
| Naphtalene (C10H8) | 127.70 | 2.95 | 377.07 | 4.4232 |
| Turpentine (C10H16) | 135.70 | 2.77 | 377.07 | 4.7003 |
| Dry air | 28.87 | 13.06 | — | 1.0000 |
EMERALD-GREEN: ITS PROPERTIES AND MANUFACTURE.[[1]]
By ROBERT GALLOWAY, M.R.I.A.
The poisonous effects of wall-paper stained with emerald-green (aceto-arsenite of copper) appears to be a very favorite topic in many journals; it is continually reappearing in one form or another in different publications, especially medical ones; there has recently appeared a short reference to it under the title, "The Poisonous Effect of Wall-paper." As some years ago I became practically acquainted with its properties and manufacture, a few observations on these subjects may not be without interest.
In the paragraph referred to, it is stated that the poisonous effect of this pigment cannot be entirely due to its mere mechanical detachment from the paper. This writer therefore attributes the poisonous effects to the formation of the hydrogen compound of arsenic, viz., arseniureted hydrogen (AsH3); the hydrogen, for the formation of this compound, being generated, the writer thinks probable, "by the joint action of moisture and organic matters, viz., of substances used in fixing to walls papers impregnated with arsenic." In some of our chemical manuals, Dr. Kolbe's "Inorganic Chemistry," for example, it is also stated that arseniureted hydrogen is formed by the fermentation of the starch-paste employed for fastening the paper to the walls. It is perfectly obvious that the fermentation of the starch-paste must cease after a time, and therefore the poisonous effects of the paper must likewise cease if its injurious effects are caused by the fermentation. I do not think that arseniureted hydrogen could be formed under the conditions, for the oxygen compound of arsenic is in a state of combination, and the compound is in a dry solid state and not in solution and the affinities of the two elements—arsenic and hydrogen—for each other are so exceedingly weak that they cannot be made to unite directly except they are both set free at the same moment in presence of each other. Further, for the formation of this hydrogen compound by the fermentation of the starch, or by the growth of minute fungi, the entire compound must be broken up, and therefore the pigment would become discolored; but aceto-arsenite of copper
(3CuAs2O4+Cu(C2H3O 2)2)
is a very stable compound, not readily undergoing decomposition, and is consequently a very permanent color. It has also been not unfrequently stated that the injurious effects of this pigment are due to the arsenious oxide volatilizing from the other constituents of the compound. This volatilization would likewise cause a breaking up of the entire compound, and would consequently cause a discoloration of the paper; but the volatilization of this arsenic compound is in every respect most improbable.
The injurious effects, if any, of this pigment must therefore be due to its mechanical detachment from the paper; but has it ever been conclusively proved that persons who inhabit rooms the wall-paper of which is stained with emerald-green suffer from arsenical poisoning? If it does occur, then the effects of what may be termed homœopathic doses of this substance are totally different from the effects which arise from larger doses. During the packing of this substance in its dry state in the factory, clouds of its dust ascend in the air, and during the time I had to do with its manufacture I never heard that any of the factory hands suffered, nor did I suffer, from arsenical poisoning. If there is any abrasion of the skin the dust produces a sore, and also the delicate lining of the nostrils is apt to be affected. It is in this way it acts in large doses; I am therefore very skeptical as to its supposed poisonous effects when wall-paper is stained with it.
Different methods are given in works on chemistry for the manufacture of this pigment, but as they do not agree in every respect with the method which was followed in English color factories some years ago, it will be as well, for the full elucidation of the manufacture of this substance, to briefly recite some of these methods before describing the one that was, and probably is still, in use; and I will afterward describe a method which I invented, and which is practically superior to any other, both in the rapidity with which the color can be formed, and for producing it at a less cost.
It is stated in Watts' "Dictionary of Chemistry" that it is "prepared on a large scale by mixing arsenious acid with cupric acetate and water. Five parts of verdigris are made up to a thin paste, and added to a boiling solution of 4 parts or rather more of arsenious acid in 50 parts of water. The boiling must be well kept up, otherwise the precipitate assumes a yellow-green color, from the formation of copper arsenite; in that case acetic acid must be added, and the boiling continued a few minutes longer. The precipitate then becomes crystalline, and acquires the fine green color peculiar to the aceto-arsenite." I do not know from personal knowledge, but I have always understood that the copper salt employed in its manufacture in France is the acetate. This would account, in my opinion, for the larger crystalline flakes in which it is obtained in France than can be produced by the English method of manufacturing it. Cupric acetate is never employed, I believe, in England—the much cheaper copper salt, the sulphate, being always employed.
In "Miller's Chemistry" it is stated it "may be obtained by boiling solutions of arsenious anhydride and cupric acetate, and adding to the mixture an equal bulk of cold water." Why it should be recommended to add cold water, I am at a loss to understand.
In Drs. Roscoe and Schorlemmer's large work on "Chemistry," and in the English edition of "Wagner's Handbook of Chemical Technology," edited by Mr. Crookes, the process as described by Dr. Ehrmann in the "Ann. Pharm.," xii., 92, is given. It is thus stated in Wagner's work: "This pigment is prepared by first separately dissolving equal parts by weight of arsenious acid and neutral acetate of copper in boiling water, and next mixing these solutions while boiling. There is immediately formed a flocculent olive-green colored precipitate of arsenite of copper, while the supernatant liquid contains free acetic acid. After a while the precipitate becomes gradually crystalline, at the same time forming a beautiful green pigment, which is separated from the liquid by filtration, and after washing and carefully drying is ready for use. The mode of preparing this pigment on a large scale was originally devised by M. Braconnot, as follows: 15 kilos. of sulphate of copper are dissolved in the smallest quantity of boiling water, and mixed with a boiling and concentrated solution of arsenite of soda or potassa, so prepared as to contain 20 kilos. of arsenious acid. There is immediately formed a dirty greenish-colored precipitate which is converted into Schweinfurt green by the addition of some 15 liters of concentrated wood-vinegar. This having been done, the precipitate is immediately filtered off and washed."
As I have already stated, the copper salt used in the manufacture of this pigment in England is the sulphate, and it is carried out pretty much according to Braconnot's method as described by Dr Ehrmann; but any one would infer, from reading his description of the manufacturing process, that the compound, aceto-arsenite of copper, was formed almost immediately after the addition of the acetic acid, a higher or lower atmospheric temperature having no effect in hastening or retarding the formation. Furthermore, it is not stated whether the compound forms more readily in an acid or neutral solution, or whether it can or cannot be formed in a neutral one; now both these points are important to notice in describing its manufacture. As regards the former I shall notice it presently, and, as far as my knowledge extends, the pigment will not form when the solution is neutral.
The operation is conducted in the following manner in the factory: The requisite quantity of sulphate of copper is placed in a large wooden vat, and hot water added to dissolve it; the requisite quantity of arsenic (arsenious anhydride) and carbonate of soda, the latter not in quantity quite sufficient to neutralize the whole of the sulphuric acid set free from the sulphate of copper on the precipitation of the copper as arsenite, are placed in another wooden vessel; water is then added, and the formation of the arsenite of soda and its solution are aided by the introduction of steam into the liquid. When complete solution has been effected the arsenic solution is run off into the vat containing the solution of the sulphate of copper, arsenite of copper being at once precipitated. The necessary quantity of acetic acid is afterward added. In warm weather the formation of the aceto-arsenite soon commences after the addition of the vinegar; but, even in that case, it takes a week or more to have the whole of a big batch of arsenite converted into the aceto-arsenite; and perfect conversion is necessary, as the presence of a very minute quantity of unchanged arsenite lowers very much the price of the emerald pigment, and a by no means large quantity renders the pigment unsalable, owing to its dirty yellowish-green color. In cold weather a much longer time is required for its complete conversion; even at the end of a fortnight or three weeks there frequently remains sufficient unconverted arsenite to affect seriously the selling price of the color; when this occurs the manufacturer generally removes these last traces by a most wasteful method viz, by adding a quantity of free sulphuric acid. The acid of course dissolves the arsenite, but it dissolves in very much larger quantities the aceto-arsenite; and this costly solution is not utilized, but is run into the factory sewer.
By my method of manufacturing it, it can be produced in winter as well as in summer in one or two hours, and the quantity of free acid required for its formation is reduced to the lowest amount. I proceed as follows: After having dissolved in hot water the requisite quantity of cupric sulphate, I decompose one-fourth of this salt by adding just sufficient of a solution of carbonate of soda to precipitate the copper, in that quantity of the sulphate, as carbonate. I then add just sufficient acetic acid to convert the carbonate into acetate. I have now got in solution—
3CuSO4 + Cu(C2H3O2)2,
and I have to transform it into—
3CuAs2O4 + Cu(C2H3O2)2.
It is at once seen that I have got the requisite quantity of acetate formed. I next dissolve the requisite quantity of arsenious anhydride in an amount of carbonate of soda rather less than is sufficient to neutralize the acid in the remaining cupric sulphate, and I then bring the solution to or near the boiling-point by introducing steam into it; the arsenic is dissolved not in the same vessel as the copper salt, but in a separate one. When the arsenic solution is fully heated, a small current of it is allowed to flow into the vat containing the copper salts, and brisk stirring is kept up in the vat. The emerald green is at once formed; but if there should be the slightest formation of any arsenite, the flow of the arsenic solution is at once stopped until every trace of the arsenite has been converted; the arsenic solution is then allowed to flow in again, with the same precautions as before; in this way a large batch of emerald-green can he formed in one or two hours, without containing the slightest trace of the arsenite. I keep the arsenic solution near the boiling-point during the whole of the time it is flowing into the other vessel. By varying the proportions of water I could either make it coarse or fine, as I wished, which is an important matter to have complete control over in its manufacture.
Two points of interest occurred to me during the time I was occupied with the research, which I had not time to complete; one was whether the aceto-arsenite can be formed, adopting the old method for its formation, if there is more than a certain quantity of water; from some experiments I made in this direction I was inclined to the opinion it could not. I have already stated that emerald-green is soluble to a certain extent in acids, and that it is formed in a more or less acid solution; consequently a varying amount of the pigment is always lost by being dissolved in the supernatant liquid. To prevent to a certain extent this loss I precipitated the copper from it as arsenite; but I was not successful in the few experiments I had time to make on this part of the subject of reconverting the copper arsenite thus obtained into the aceto-arsenite by the addition of acetic acid.—Jour. of Science.
This substance is also known by the name Schweinfurt green.