Columns 1, 2, 3, 5, 6, 7, 8, and 9, of this table, point out the circumstances in which the experiments were made, or the result of the experiments, and require no explanation. The gases which passed through the calorimeter having been measured at temperatures somewhat different, we have in the fourth column, in order to make them more capable of comparison with each other, brought the numbers of the second column to what they would have been if we had measured all the gases at the freezing temperature. The sixth column indicates the stationary temperature to which each current of gas brought the calorimeter. The reader will recollect that we determined this temperature by means of two series of observations, one in which the calorimeter being a little below this stationary temperature, the rate of the elevation of its temperature was observed; another in which the calorimeter being a little elevated above this temperature, the rate of its cooling was equally observed. To form an idea of the way of obtaining this determination, the reader may consult Note 2 at the end of this paper, in which are given the details of the first experiment made upon atmospherical air. The numbers composing the tenth column have been calculated on the supposition that the effect produced upon the calorimeter was proportional to the quantity of gas which passed through it, and to the number of degrees of heat lost by the gas -a supposition that cannot be disputed when it relates to so small differences. The numbers composing the eleventh column were calculated by means of a formula, which will be explained in Section V, which contains the experiments made upon the specific heat of air subjected to different pressures. This last column, expressing the stationary temperature at which each current maintained the calorimeter, the circumstances being exactly the saine, we are entitled to conclude, from the principles which we have explained, that the numbers which it contains are proportional to the specific heat of the gases. Hence the specific heat of atmospheric air being 1.000, that of examined is as follows: the gases The specific heat of azotic gas was not determined by a direct experiment. We have considered it as equal to that of the same bulk of atmospherical Account of a singular Effect of Voltaic Electricity on a slender Platina Wire. By George John Singer, Lecturer on Expe→ rimental Philosophy. DURING a series of experiments on the effect of various mediums on the ignition of platina by voltaic electricity, a wire of that metalth of an inch diameter and three inches long was extended in the centre of a globular receiver, which contained about 22 cubic inches of hydrogen gas. The wire was then placed in the circuit of a voltaic battery of such power as (it had been previously ascertained) would produce a white heat on a similar length when exposed in the open atmosphere. of On completing the circuit there was not any appearance ignition, but the wire vibrated strongly, and suddenly exhibited a most extraordinary result; near two inches of its length being split into a bundle of minute fibres, irregularly diverging from a central thicker portion, and continuing attached to the remaining wire at each extremity, so as to assume the form of a lengthened spheroid, corresponding in appearance to an electrified bundle of threads having their ends fastened together. The fibres were so minute as to be scarcely visible to the unassisted eye, when viewed separately. One of these being compared under a microscope with a fine wire drawn by Dr. Wollaston's process, was found to have a diameter of less than the 5000th part of an inch. In the course of innumerable experiments on the fusion of wires by common electricity, I have observed no similar effect; air; because it constitutes ths of air, and because the specific heat of oxygen differs but little from that of air. To calculate the specific heats of the same weights of the gases we have employed the specific gravity of olefiant gas given by Saussure in the Ann. de Chim. Ixxviii, 57, and the specific gravity of the other gases given in the Mem. d'Arcueil, ii, 253, but I am informed by Mr. Cuthbertson that he has occasionally splintered iron wires; and I find that Mr. Brook noticed the same circumstance with steel wire, in two experiments out of 73, published in the year 1797. The splinters he produced are described as about th of an inch long. I shall not at present speculate on this phenomenon, which seems to prove, by the expansive effect produced, that in certain cases at least electricity passes through the substance of solid matter; and in such passage displays most unequivocally the action of a material power. I remain, Sir, your's, &c. Princes-street, Cavendish-square, G. J. SINGER. ARTICLE XI. On the Daltonian Theory of Definite Proportions in Chemical Compounds. By Thomas Thomson, M.D. F.R.S. (Continued from p. 171.) We have no data for determining the composition of the phosphurets, those only excepted which have been given in a preceding part of the table. No metallic carburets are known to exist. There can be little doubt that plumbago is in fact a pure charcoal, and that the small quantity of iron which it contains is only accidentally present. A carburet of iron, supposing it composed of an atom of each element, would consist of Iron 89.875 10.125 100.000 But we are not acquainted with any such compound. Messrs. Allen and Pepys found that 100 parts of plumbago, when burnt, left a residue of 5 parts. If we suppose this residue to be peroxide of iron, it will be equivalent to 3.45 parts of iron. According to this statement the plumbago consisted of 96·55 parts of charcoal and 3·45 parts of iron. This amounts to about 248 atoms of carbon combined with 1 atom of iron. We may be quite certain that so great a number of atoms of carbon never could come in contact with one atom of iron, and that therefore such a compound cannot exist: besides, we are not sure that this residue consisted of oxide of iron. Schräder, in an analysis of plumbago inserted in the Annals of Philosophy, vol. i. p. 294, has shown that this residue is of a complicated nature, consisting of oxide of iron, oxide of titanium, silica, and alumina. From Mr. Mushet's experiments it seems to follow that the compound of iron and carbon, the hardness of which is a maximum, the colour white, and the texture crystallized, is a compound of about 7 atoms of iron and 1 of carbon. Steel, if any confidence can be put in the experiments hitherto made to determine its composition, seems to consist of I atom of carbon united with from 10 to 13 atoms of iron, according to the nature of the steel: but these chemical analyses are still too imperfect to permit us to place the different varieties of steel and cast-iron in our table. I shall proceed therefore to the salts, many of which have been analysed with great care, and which constitute the best established department of chemical science. Genus I.-Sulphates. Sulphuric acid, it will be seen from our table (Annals of Philosophy, vol. ii. p. 44), is composed of 1 atom of sulphur and 3 atoms of oxygen, and the weight of an integrant particle of it is 5.000. Number of 164. Sulphate of potash .....1 s + 1 p 2 so .20.764 c C 7.284 d 165. Supersulphate of potash. .2s+1 p......16.000 b 166. Sulphate of soda.......1 s + 167. Sulphate of ammonia...1 s + 2 a a I found by a careful analysis of sulphate of potash, fused previously in a platinum crucible, that 100 parts of it contained 42.2 of acid and 501 of potash. Now 56: 42·2: 50·62; which corresponds with the analysis very nearly. In giving the weight of an integrant particle of the salts I have been obliged to omit the water of crystallization, because it has been accurately determined in a very small number of salts only. b Dr. Wollaston has shown that in this salt the quantity of acid is just double what exists in the sulphate. C According to Wenzel, sulphate of soda is composed of 100 acid 78-32 base; according to Berzelius, of 100 acid + 79.34 base. Now 5: 7.882 :: 100:157·64, and Now this is the mean of the two experiments. 157.64 = 78.82. d According to Berzelius (Gilbert's Annalen, xl. 282), this salt is composed of 100 acid + 42-561 ammonia. Now 100: ... Number of 168. Sulphate of magnesia .1 s + I m 169. Sulphate of lime.... 1 s + 1 l 170. Sulphate of barytes 1 s + 1 b .14.731 1 str 1 a 7.136 i 9.272 2 a 171. Sulphate of strontian ..,1 s + ..13.400 8.600 ..10.656 .4 s + 2 a + 1p 30-2721 42-561 :: 5 : 2-128, and 2-128 = 1.064, which differs but little 2 from the weight of an atom of ammonia. e According to Dr. Henry, sulphate of magnesia is composed of 100 acid + 47.36 base. This exactly agrees with the statement in the table: nor could it be otherwise, as the weight of magnesia was estimated from that analysis. Berzelius makes it 100 acid + 50'06 base. (Gilbert's Annalen, vol. xl. p. 256) f This coincides almost exactly with the analysis of Berzelius. He found sulphate of lime composed of 100 acid + 72-41 base. Now 5 : 3·620 :: 100: 72·40. This coincides with the analysis of Berzelius, who found sulphate of barytes composed of 100 acid + 194 base. Now 59731 :: 100; 194 62. The weight of strontian was deduced from the supposition that the sulphate of strontian is composed of 100 acid + 138 base. Of course the number in the table is conformable to that supposition. According to Berzelius, sulphate of alumina is composed of 100 acid + 42.722 alumina. (Gilbert's Annalen, vol. xl. p. 262.) Supposing the salt composed as in the table, the number representing an atom of alumina should be 2·136. Neither this nor the two following salts have been hitherto analysed; but I have inserted them in the table, stating their composition from the very probable analogy that they are composed of 1 atom of acid united to 1 atom of base; this being the case with all the preceding neutral salts in the table, except the sulphate of soda. This seems to be a combination of an integrant particle of three different salts: namely, 1st. Sulphate of potash, composed of 1 s + 1 p. 2d. Sulphate of alumina, composed of 1 s + 1 a. 3d. Supersulphate of alumina, composed of 2 s + 1 a. These |