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| | | | |
| | | Volumes of | |
| | Tem- | Acetylene | |
| Solvent. |perature.|dissolved by| Authority. |
| | | 100 Vols. | |
| | | of Solvent.| |
|___________________________|_________|____________|__________________|
| | | | |
| | Degs. C | | |
| Acetone . . . . | 15 | 2500 | Claude and Hess |
| " . . . . | 50 | 1250 | " |
| Acetic acid; alcohol . | 18 | 600 | Berthelot |
| Benzoline; chloroform . | 18 | 400 | " |
| Paraffin oil . . . | 0 | 103.3 | E. Muller |
| " . . . | 18 | 150 | Berthelot |
| Olive oil . . . . | -- | 48 | Fuchs and Schiff |
| Carbon bisulphide . . | 18 | 100 | Berthelot |
| " tetrachloride . | 0 | 25 | Nieuwland |
| Water (at 4 65 atmospheres| | | |
| pressure) . . | 0 | 160 | Villard |
| " (at 755 mm. pressure)| 12 | 118 | Berthelot |
| " (760 mm. pressure) . | 12 | 106.6 | E. Müller |
| " " . | 15 | 110 | Lewes |
| " " . | 18 | 100 | Berthelot |
| " " . | -- | 100 | E. Davy (in 1836)|
| " " . | 19.5 | 97.5 | E. Müller |
| Milk of lime: about 10 | | | |
| grammes of calcium hy- | 5 | 112 | Hammerschmidt |
| droxide per 100 c.c. . | | | and Sandmann |
| " " " | 10 | 95 | " |
| " " " | 20 | 75 | " |
| " " " | 50 | 38 | " |
| " " " | 70 | 20 | " |
| " " " | 90 | 6 | " |
| Solution of common salt,5%| 19 | 67.9 | " |
| (sodium chloride) " | 25 | 47.7 | " |
| " 20%| 19 | 29.6 | " |
| " " | 25 | 12.6 | " |
| "(nearly saturated, | | | |
| 26%) . . | 15 | 20.6 | " |
| "(saturated, sp. gr.| | | |
| 1-21) . . | 0 | 22.0 | E. Müller |
| " " " | 12 | 21.0 | " |
| " " " | 18 | 20.4 | " |
| Solution of calcium | | | Hammerschmidt |
| chloride (saturated) . | 15 | 6.0 | and Sandmann |
| Bergé and Reychler's re- | | | |
| agent . . . . | -- | 95 | Nieuwland |
|___________________________|_________|____________|__________________|
SOLUBILITY.--Acetylene is readily soluble in many liquids. It is desirable, on the one hand, as indicated in Chapter III., that the liquid in the seals of gasholders, &c., should be one in which acetylene is soluble to the smallest degree practically attainable; while, on the other hand, liquids in which acetylene is soluble in a very high degree are valuable agents for its storage in the liquid state. Hence it is important to know the extent of the solubility of acetylene in a number of liquids. The tabular statement (p. 179) gives the most trustworthy information in regard to the solubilities under the normal atmospheric pressure of 760 mm. or thereabouts.
The strength of milk of lime quoted in the above table was obtained by carefully allowing 50 grammes of carbide to interact with 550 c.c. of water at 5° C. A higher degree of concentration of the milk of lime was found by Hammerschmidt and Sandmann to cause a slight decrease in the amount of acetylene held in solution by it. Hammerschmidt and Sandmann's figures, however, do not agree well with others obtained by Caro, who has also determined the solubility of acetylene in lime-water, using first, a clear saturated lime-water prepared at 20° C. and secondly, a milk of lime obtained by slaking 10 grammes of quicklime in 100 c.c. of water. As before, the figures relate to the volumes of acetylene dissolved at atmospheric pressure by 100 volumes of the stated liquid.
_________________________________________________
| | | |
| Temperature. | Lime-water. | Milk of Lime. |
|_______________|_______________|_________________|
| | | |
| Degs C. | | |
| 0 | 146.2 | 152.6 |
| 5 | 138.5 | -- |
| 15 | 122.8 | 134.8 |
| 50 | 43.9 | 62.6 |
| 90 | 6.2 | 9.2 |
|_______________|_______________|_________________|
Figures showing the solubility of acetylene in plain water at different temperatures have been published in Landolt-Börnstein's Physico- Chemical Tables. These are reproduced below. The "Coefficient of Absorption" is the volume of the gas, measured at 0° C. and a barometric height of 760 mm. taken up by one volume of water, at the stated temperature, when the gas pressure on the surface, apart from the vapour pressure of the water itself, is 760 mm. The "Solubility" is the weight of acetylene in grammes taken up by 100 grammes of water at the stated temperature, when the total pressure on the surface, including that of the vapour pressure of the water, is 760 mm.
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| | | |
| Temperature. | Coefficient of | Solubility. |
| | Absorption. | |
|______________|________________|_____________|
| | | |
| Degs. C. | | |
| 0 | 1.73 | 0.20 |
| 1 | 1.68 | 0.19 |
| 2 | 1.63 | 0.19 |
| 3 | 1.58 | 0.18 |
| 4 | 1.53 | 0.18 |
| 5 | 1.49 | 0.17 |
| 6 | 1.45 | 0.17 |
| 7 | 1.41 | 0.16 |
| 8 | 1.37 | 0.16 |
| 9 | 1.34 | 0.15 |
| 10 | 1.31 | 0.15 |
| 11 | 1.27 | 0.15 |
| 12 | 1.24 | 0.14 |
| 13 | 1.21 | 0.14 |
| 14 | 1.18 | 0.14 |
| 15 | 1.15 | 0.13 |
| 16 | 1.13 | 0.13 |
| 17 | 1.10 | 0.13 |
| 18 | 1.08 | 0.12 |
| 19 | 1.05 | 0.12 |
| 20 | 1.03 | 0.12 |
| 21 | 1.01 | 0.12 |
| 22 | 0.99 | 0.11 |
| 23 | 0.97 | 0.11 |
| 24 | 0.95 | 0.11 |
| 25 | 0.93 | 0.11 |
| 26 | 0.91 | 0.10 |
| 27 | 0.89 | 0.10 |
| 28 | 0.87 | 0.10 |
| 29 | 0.85 | 0.10 |
| 30 | 0.84 | 0.09 |
|______________|________________|_____________|
Advantage is taken, as explained in Chapter XI., of the high degree of solubility of acetylene in acetone, to employ a solution of the gas in that liquid when acetylene is wanted in a portable condition. The solubility increases very rapidly with the pressure, so that under a pressure of twelve atmospheres acetone dissolves about 300 times its original volume of the gas, while the solubility also increases greatly with a reduction in the temperature, until at -80° C. acetone takes up 2000 times its volume of acetylene under the ordinary atmospheric pressure. Further details of the valuable qualities of acetone as a solvent of acetylene are given in Chapter XI., but it may here be remarked that the successful utilisation of the solvent power of acetone depends to a very large extent on the absolute freedom from moisture of both the acetylene and the acetone, so that acetone of 99 per cent. strength is now used as the solvent.
Turning to the other end of the scale of solubility, the most valuable liquids for serving as seals of gasholders, &c., are readily discernible. Far superior to all others is a saturated solution of calcium chloride, and this should be selected as the confining liquid whenever it is important to avoid dissolution of acetylene in the liquid as far as may be. Brine comes next in order of merit for this purpose, but it is objectionable on account of its corrosive action on metals. Olive oil should, according to Fuchs and Schiff, be of service where a saline liquid is undesirable; mineral oil seems useless. Were they concordant, the figures for milk of lime would be particularly useful, because this material is naturally the confining liquid in the generating chambers of carbide-to-water apparatus, and because the temperature of the liquid rises through the heat evolved during the generation of the gas (vide Chapters II. and III.). It will be seen that these figures would afford a means of calculating the maximum possible loss of gas by dissolution when a known volume of sludge is run off from a carbide-to- water generator at about any possible temperature.
According to Garelli and Falciola, the depression in the freezing-point of water caused by the saturation of that liquid with acetylene is 0.08° C., the corresponding figure for benzene in place of water being 1.40° C. These figures indicate that 100 parts by weight of water should dissolve 0.1118 part by weight of acetylene at 0° C., and that 100 parts of benzene should dissolve about 0.687 part of acetylene at 5° C. In other words, 100 volumes of water at the freezing-point should dissolve 95 volumes of acetylene, and 100 volumes of benzene dissolve some 653 volumes of the gas. The figure calculated for water in this way is lower than that which might be expected from the direct determinations at other temperatures already referred to; that for benzene may be compared with Berthelot's value of 400 volumes at 18° C. Other measurements of the solubility of acetylene in water at 0° C. have given the figure 0.1162 per cent. by weight.
TOXICITY.--Many experiments have been made to determine to what extent acetylene exercises a toxic action on animals breathing air containing a large proportion of it; but they have given somewhat inconclusive results, owing probably to varying proportions of impurities in the samples of acetylene used. The sulphuretted hydrogen and phosphine which are found in acetylene as ordinarily prepared are such powerful toxic agents that they would always, in cases of "acetylene" poisoning, be largely instrumental in bringing about the effects observed. Acetylene per se would appear to have but a small toxic action; for the principal toxic ingredient in coal-gas is carbon monoxide, which does not occur in sensible quantity in acetylene as obtained from calcium carbide. The colour of blood is changed by inhalation of acetylene to a bright cherry-red, just as in cases of poisoning by carbon monoxide; but this is due to a more dissolution of the gas in the haemoglobin of the blood, so that there is much more hope of recovery for a subject of acetylene poisoning than for one of coal-gas poisoning. Practically the risk of poisoning by acetylene, after it has been purified by one of the ordinary means, is nil. The toxic action of the impurities of crude acetylene is discussed in Chapter V.