A new system of chemical philosophy, Volume 2, Part 1

by John Dalton

2 and 3. Phosphurets of
carbone and sulphur.

See Vol. 1. page 464.

4. Phosphuret of lime.

This compound may be formed by subliming phosphorus in a glass tube containing small fragments of recently calcined lime, heated to a low red. The sublimed phosphorus coming into contact with the hot lime, the two unite with a vivid glow, and in due time mutual saturation is produced. The result is a dry, hard compound of a deep brown or reddish colour, which on cooling must be put into a bottle and well corked, if not intended for immediate use, as it soon changes by the action of atmospheric air and moisture. With this precaution, I have reason to think it may be kept unimpaired for years.

As far as I know, no experiments have been published relating to the proportion in which phosphorus and lime unite. M. Dulong, in a valuable paper on the combinations of phosphorus and oxygen, in the Memoires de la Société d’Arcueil, Vol. 3. (1817,) has given some account of his experiments on the earthy phosphurets; but it is to be regretted that he has given none on the proportions of their elements.

In order to ascertain the phosphorus, I put 10 grains of well preserved phosphuret of lime, into 1000 grains of liquid oxymuriate of lime, such that by previous trials I knew would impart 3.5 grains of oxygen; to this mixture a quantity of muriatic acid was put, sufficient to engage the lime; the phosphuretted hydrogen disengaged, was of course made to pass through the liquid as it was generated, and became oxidized, so as to lose its gaseous form; the surplus gas was prevented from escaping by an inclination of the bottle; it was 45 grain measures only, and of this 30 were found to be pure hydrogen, and the rest atmospheric air detached from the water; these 30 measures were the free hydrogen, which would have been mixed with the phosphuretted hydrogen, in the ordinary way. In due time, the whole of the phosphuret of lime was dissolved. The liquid was strongly acid, and manifested no smell of oxymuriatic acid, a proof that it was all decomposed. To this were added 70 more of the oxymuriate of lime before the smell of it was permanently developed. The liquid was next saturated with lime water, and the phosphate of lime carefully collected and dried; when heated to a low red it weighed 12 grains, and consisted, according to my estimate of this compound, of 6— grains of phosphoric acid and 6 + grains of lime. The 6— grains of acid contained 2.4 phosphorus and 3.5 of oxygen. It must be remembered that 10 grains of phosphuret yield about 500 measures of phosphuretted hydrogen, and these contain 650 measures of hydrogen, which last is also oxidized at the expence of the oxymuriatic acid; but then there is an equivalent of oxygen from the water, so that this does not influence the calculation for oxygen. There appears then to be only an excess of .24 grains of oxygen unaccounted for, (arising from the additional 70 of oxymuriate of lime), which is as little as can be expected in such an experiment. If the phosphorus amount to 24 per cent. we may reasonably infer that the remainder (76) is mostly lime, though I have not been able to detect above 60. Now if an atom of phosphorus weigh 9⅓ and one of lime 24, the due proportion of the protophosphuret of lime would be 28 phosphorus and 72 lime; but when the article is made for sale, it is more likely to find a defect than an excess of phosphorus.

According to Dulong, when the earthy phosphurets are decomposed by water, phosphuretted hydrogen and subphosphorous acid are formed. I believe this determination is right; for I find at most only ⅓ of the above proportion of phosphorus in the phosphuretted hydrogen yielded by 10 grains of the phosphuret of lime; the remaining ⅔ seem to rest in the liquid in combination with the oxygen and lime; that is, 1 atom of hydrogen combines with 1 of phosphorus, and 1 of oxygen with 2 of phosphorus. Notwithstanding this, the phosphoric acid produced from the residue by means of oxymuriate of lime, does not in general correspond to the above quantity. Perhaps this loss may be owing to the phosphorus carried over in mechanical suspension by the gas.

M. Dulong observes, that even the earthy subphosphites are very soluble; this did not appear to me to be the case with that of lime: 10 grains of phosphate of lime, that had been exposed for 20 minutes to the air, were put into a gas bottle filled with 400 grains of water; this was kept at nearly the boiling heat for an hour, when 725 grain measures of gas were produced, and some phosphorus was carried over with it into the receiving bottle and bason of water. The gas being analysed, was found to consist of 62 per cent. phosphuretted hydrogen, 33 hydrogen and 5 common air. The 400 grains of water in the gas bottle treated with oxymuriate of lime, and then with lime water, scarcely gave any appreciable quantity of phosphate of lime. The insoluble residue when dried yielded 9 grains. This dissolved in muriatic acid left a fraction of a grain of dirty yellow powder, which indicated some phosphorus; and the muriate of lime indicated about 6 grains of lime.

5. Phosphuret of barytes.

The combination of phosphorus and barytes may be effected in the same way as the foregoing, and the compound has the same appearance. According to Dulong, who has examined this phosphuret with particular attention, it gives out phosphuretted hydrogen when dropped into water, the same as that of lime. When the gas ceases to be given out, a powder remains completely insoluble in water, of a variable colour, yellow, grey or brown. It is not altered by the air; but it gives out a slight phosphoric flame when heated. Dilute nitric or muriatic acid, dissolves nearly the whole with a trace of phosphuretted hydrogen, and leaves only a few atoms of greenish yellow powder, soluble in oxymuriatic acid. The part dissolved by the acids being precipitated by ammonia, gives phosphate of barytes. From these facts he infers that the residue insoluble in water, consists of a small portion of phosphuret of barytes with excess of base, and phosphate of barytes. The water in which the phosphuret was decomposed, contains most of the barytes; carbonic acid produces a slight precipitate, and then leaves a neutral liquid containing the subphosphate of barytes, which appears to be a very soluble salt. Sulphuric acid throws down the barytes and leaves the subphosphorous acid in the liquid.