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t in which s has the same signification as in equation (1); L is the latent heat of solution of a molecule of the dissolved substance in a large amount of the nearly saturated solution ; t is the temperature of saturation, and t the point of fusion. This formula leads at once to the conclusion that "the normal curve of solubility of a given boily should be the same in all solvents, because the equation contains no term having reference to the solvent."
In a subsequent “ Note,” Le Chatelier communicated the solubilities of sodium chloride in fused sodiun carbonate, and barium chloride; also of lithium sulphate in fused calcium sulphate, lithium carbonate, and sodium sulphate, these data being found entirely in accordance with the law enunciated.
Veither Schroeder nor Le Chatelier claims that the law in question expresses more than an approximate relation between the quantities upon which it has a bearing. Le Chatelier as: cribes any exceptions to its generality to differences in the latent heats of solution, which may vary from solvent to sol
The law should, then, be restricted in its government to chemically similar compounds, and, indeed, it is seen that the compounds, experimented upon by each observer, belong to the same general classes,--the normal organic preparations (Schroeder), and the salts (Le Chatelier). But when we consider groups of chemical substances of differing natures, we perceive that all the regularity of the phenomenon, which has been formulated into a law, disappears; the very fact, that there exist substances, which do not unite with certain others to form the homogeneous mixtures commonly called solutions, is sufficient to warrant the restriction of the law to quite narrow limits. Nearly all inorganic salts are not at all
, or, at most, but sparingly soluble in the vast number of organic liquids. Unhappily, our quantitative knowledge of the solubility of salts in organic liquids is very limited; yet perhaps enough data may be collected to permit of the drawing of theoretic conclusions. The object of this paper is to discuss in the light of the Schroeder-Le Chatelier law, the data we possess on the solubility of inorganic salts in normal organic liquids. The importance of this law, which, in its enunciation, is one of the widest-reaching in the domain of solutions, makes it very desirable that it be applied to all cases, in order that it may be ascertained to what degree its approximation towards truth may come.
The greater part of the determinations of the solubilities of salts in organic liquids has been done with the alcohols, espec
Am. JOUR. Sci.-THIRD SERIES, VOL. XLIX, No. 289 -Jan., 1895.
ially ethyl alcohol, as solvents. The choice of such solvents is unfortunate, since, aside from the difficulty experienced in getting and preserving them in a state of purity, they are made up of associated molecules ; and this circumstance introduces very serious complications, for not only is the relative proportion of associated molecules different at different temperatures, but also the dissolved substance must have some influence on the degree of molecular association of the solvent, the combined result being that the nature of the solvent varies infinitely. Accordingly, from reasons that are obvious, only “normal” liquids, that is, such liquids as possess the same molecular mass in the liquid as in the gaseous state, will be considered in what follows. By thus eliminating the difficulty arising from the use of associated liquids, it may be possible to get matters into a clearer light. In what follows, no pretensions are made to discuss all the data on the solubility of salts in organic liquids; only such data as seem to have the stamp of reliability will be considered.
Étard* in the course of his extended investigations on the solubility of substances, determined through wide ranges of temperature the solubilities of the salts, mercuric and cupric chlorides, in a number of normal liquids, mostly esters. As in this case the solvents are chemically very similar, it seems likely that, if the above law is at all applicable to the solubilities of salts in organic liquids, Étard's data will permit of its ascertainment.
According to Étard, the solubility of corrosive sublimate in ethyl ether is as follows,—the numbers directly under the temperatures being the number of parts of the salt contained in 100 parts of the saturated solution: -47° -40° -35°
-19° 5.6 5.8 6:1 5.9 5.6 5.8 5.8 8.4 8.7
From -47° to +60°, that is, throughout a temperature interval of more than 100°, Étard states that the solubility is the same; the average of the above first seven data is 5:8, which represents the mean solubility for the temperature interval just mentioned. If this be recalculated in molecular proportions, it comes out that 100 molecules of the saturated solution contain 1.65 molecules (of normal size, i. e. corresponding to the formula HgCl,) of the salt. Above 60°, however, the solubility increases with rise of temperature (see Table I for recalculated data).
Similar phenomena were observed in the case of the solubility of corrosive sublimate in acetic ether, the data of which are these :
* Ann. de chim. et de phys., VII, ii, 560.
In an interval of more than 70°, the solubility seems to be constant, 100 parts of the saturated solution containing on an average 40-0 parts of salt, or, calculated in molecular proportions, 17.80 molecules of salt are in 100 molecules of the solution. Above 40° the solubility augments with rise of temperature as shown thus :
Étard gives also the solubility of mercury chloride as well as of copper chloride in other ethers ; I will not reproduce the data as presented by him, but will throw them into tabular form, after having made the calculations necessary to change them into solubilities defined by the ratio of dissolved molecules to the total number of molecules contained in the solution.
Solubility of Mercuric Chloride in Organic Liquids. Yames of Liquids,
-50° -17° -40° -35° -30° -20° -19° -14° -6° -3° -0° +7° 13° 19° Ethyl Ether, 1.65 1.65 1.65 1.65
1.65 Ethyl formiate,
10:43 Ethyl acetate, 17.80
17.80 Methyl acetate,
16:51 Ampl acetate, Ethyl butyrate,
TABLE I, Continued. James of Liquids,
20° 22 24° 45° 46' 48° 55° 66° 71° 83° 100° 115° 131° 150° Ethyl Ether,
2:45 2:52 Ethyl forriate,
10:48 10.48 Ethyl acetate.
25.02 30.09 Methyl acetate,
16:23 Amyl acetate
9.82 E:151 Butyrate, 5.81
24° 37° 40° 50° 72° Ethyl formiate.. 5.88
4:08 Ethyl acetate....
The data given in Tables I and II cannot be said to confirm the predictions of the law under discussion. The solubility of mercuric chloride in acetic ether and in ethyl formiate is indeed nearly the same ; and so is that of copper chloride in acetic ether, and of mercuric chloride in ethyl ether. These
cases are, however, exceptional, and can be as likely due to chance as to law. Now, as it may be laid down as a general rule that, no matter in how many instances a “law of Nature" may be confirmed, one exception is sufficient to disprove that generality which is taken to be the very essence of law, it is apparent that the truth of the “law” in the case in hand is very doubtful.
Arctowski* has investigated what may be termed the complement of the case studied by Étard (loc. cit.), for he determined the solubility of three very similar -as regards their chemical constitution---salts, viz: the chloride, bromide, and iodide of mercury, in carbon disulphide. Arctowski communicates his results in the same form as does Étard. To permit of direct comparison with our “ law," I have recalculated his results in molecules, the data being given in Table III.
TABLE III. Solubility of the IIalide Salts of Mercury in Carbon Bisulphide. Mercuric. – 767° -21° – 101° 0° 8' 131 191° 25° 29° Chloride, 0.003 0.004 0.005
(.099 0.011 0:016 Bromide, 0.011 0:018 0.024 0.029 0.038
0.011 Iodide, 0.008 0.013 0·017 0·029 0.039 0.044 0·050 0.056 0.079
Here again we see no confirmation of the “law” in question. The solubilities of the salts are in direct proportion to their molecular masses, and the curves with temperatures on axis of abscissas and solubilities on axis of ordinates are very nearly parallel.
In order to increase our knowledge of the solubilities of salts in organic liquids, and to augment our store of data with which to compare the law in question, I have made a number of determinations of the solubility of several salts in benzene and ethyl ether; the results of this work are given in Tables IV and V.
TABLE IV. Solubility of Cadmium Iodide, Mercuric Chloride, and Silver Nitrate in Benzene.
Temperatures. 109.7 11°:4 16° 0 35° 0 3898 40°.5 Cadmium iodide,
0:01 0.02 Mercurie chloride, 0.11 0:12
0.23 0.25 Silver nitrate,
0:05 These data also cannot be said to be favorable to the law.
* Zeitschr. f, anorgan. Chemie, v, 263, 1894.
It is evident from all the data which have been exhibited in the preceding tables, that no trace of the applicability of the Schroeder-Le Chatelier law is to be found. It may, now, be urged that in our definition of solubility as the number of molecules of dissolved substance contained in 100 molecules of the solution, the value of the molecular mass of the dissolved substance has rather arbitrarily been assumed to be equal to that which it has in the gaseous condition, although nothing positive in regard to the real size of the molecule in the dissolved state is known ; if the molecular mass of the substance in the gaseous state be doubled, tripled, quadrupled, etc., when it is in solution, the number, expressing the solubility in the manner here adopted, must be changed correspondingly. But even if our knowledge of the molecular state of salts dissolved in organic liquids was sufficient to permit of the introduction of this correction, its amount would not be large enough to account for the very considerable differences in solubility of even the same salt in different, yet chemically similar, organic solvents, as any one can convince himself by a simple calculation. We conclude then, that the law enunciated by Schroeder, and by Le Chatelier, although approximately true for the cases investigated by them, is not applicable to the case of inorganic salts in normal organic solvents.
Chicago, November 26th, 1894.
Art. V.-Preliminary Notice of the Plymouth Meteorite;
by HENRY A. WARD,
The Plymouth meteorite was found in the year 1893 by Mr. John Jefferson Kyser, while plowing in a field on his farm about five miles southwest of the town of Plymouth, Marshall County, Indiana. Mr. Kyser had, about the year 1872, found in the same field another, larger mass of the same iron. This mass was pear-shaped, about four feet in length by three feet in its widest diameter, narrowing to six or eight inches at its upper end.
It lay for a year or two so near the surface of the ground as to be seriously annoying in plowing the field. On that account, Mr. Kyser, aided by his son, dug a deep hole by the side of the mass and buried it to the depth of one and onehalf to two feet beneath the surface, where it should thenceforth do no more damage.
The account of this I had last June from the son, Mr. John M. Kyser, now city clerk of Plymouth. Mr. Kyser well remembers the circumstance of the finding of the large piece and assisting his father in burying the same; and he further