11. On the Fluidity of Sulphur and Phosphorus at common temperatures, by Mr. Faraday.
Not being able to obtain access to the original journal, I shall quote M. Bellani’s very curious experiments from the Bulletin, in which they appear to be fully described. “The property which water possesses, of retaining its fluid states, when in tranquillity, at temperatures 10° or 15° below its freezing point, is well known; phosphorus behaves in the same manner; sometimes its fluidity may be retained at 13° (centigrade?) for a minute, an hour, or even many days. What is singular is, that, though water cooled below its freezing point, congeals easily upon slight internal movement, however communicated, phosphorus, on the contrary, sometimes retains its liquid state even at 3°, even though it be shaken in a tube or poured upon cold water. But, as soon as it has acquired the lowest temperature which it can bear without solidifying, the moment it is touched with a body at the same temperature, it solidifies so quickly, that the touching body cannot penetrate its mass. If the smallest morsel of phosphorus is put into contact with a liquified portion, the latter infallibly solidifies, though it be only a single degree below the limit of temperature necessary; this does not always happen when the body touching it is heterogeneous.
“Sulphur presented the same phenomena as phosphorus; fragments of sulphur always produced the crystallization of cold fluid portions. Having withdrawn the bulb of a thermometer which had been plunged into sulphur at 120°, it came out covered with small globules of sulphur, which remained fluid at 60°; and having touched these one after another with a thread of glass, they became solid: although several seemed in contact, yet it required that each [p470] should be touched separately. A drop of sulphur, which was made to move on the bulb of the thermometer, by turning the instrument in a horizontal position, did not congeal until nearly at 30°; and some drops were retained fluid at 15°, i. e. 75° of Reaumur below the ordinary point of liquefaction.”
The Bulletin Universel then proceeds to describe some late and new experiments of M. Bellani, on the expansion in volume of a cold dense solution of sulphate of soda during the solidification of part of the salt in it. The general fact has, however, been long and well known in this country and in France; and the particular form of experiment described is with us a common lecture illustration. The expansion, as ascertained by M. Bellani, is 287 of the original volume of fluid.
According to the Bulletin, M. Bellani also claims, though certainly in a much less decided manner than the above, the principal ideas in a paper which I have published on the existence of a limit to vaporization, and I referred back to the Giornale di Fisica for 1822, (published prior to my paper,) for the purpose of rendering justice in this case also. Here, however, the contact of our ideas is so slight, and for so brief a time, that I shall leave the papers in the hands of the public without further remarks. It is rather curious to observe how our thoughts had been at the same time upon the same subject. Being charged in the Bulletin with quoting an experiment from a particular page in M. Bellani’s memoir, (which I did from another journal, in which the experiment only was described,) I turned to the original place, and there, though I found the experiment I had transferred, I also found another which I had previously made on the same subject, and which M. Bellani had quoted.
I very fully join in the regret which the Bulletin Universel expresses, that scientific men do not know more perfectly what has been done, or what their companions are doing; but I am afraid the misfortune is inevitable. It is certainly impossible for any person who wishes to devote a portion of his time to chemical experiment, to read all the books and papers that are published in connexion with his pursuit; their number is immense, and the labour of winnowing out the few experimental and theoretical truths which in many of them are embarrassed by a very large proportion of uninteresting matter, of imagination, and of error, is such, that most persons who try the experiment are quickly induced to make a selection in their reading, and thus inadvertently, at times, pass by what is really good.
[130] Quarterly Journal of Science, xxi. 392.
[131] The Italian Journal has not yet arrived in this country.
12. Separation of Selenium from Sulphur.
Some of the sulphuret of selenium from Lukawitz, in Bohemia, was dissolved in potash, and the solution converted into hyposulphite by exposure to the air at the temperature of 65° F.; 0.1125 of the sulphuret experimented with were precipitated, and found to be pure selenium. The solution being of a deeper red colour than that of the common sulphuret, a piece of sulphur was put into it, and the whole boiled for a moment; a quarter of a grain of selenium, perfectly free from sulphur, was precipitated.