Contributions to the history of the phosphorus-bases / by Augustus William Hofmann.

  • Hofmann, August Wilhelm von, 1818-1892.
Date:
1861
Catalogue details

Licence: Public Domain Mark

Credit: Contributions to the history of the phosphorus-bases / by Augustus William Hofmann. Source: Wellcome Collection.

Provider: This material has been provided by King’s College London. The original may be consulted at King’s College London.

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    observed occasionally small, well-defined yellow crystals disseminated among the mixture of white and red needles, which are deposited when the digestion-tubes are allowed to cool, before the transformation is terminated. The yellow crystals appeared in greater quantity towards the close of the operation, and were found to be a secondary product formed by the action of the sulphuretted hydrogen, which is generated in the last stage of the process. I have since learnt to prepare the yellow crystals by a simpler and more definite method. This remarkable compound has become the starting-point of a new inquiry, the result of which I reserve for a later communication. The formation of the red crystals by the union of triethylphosphine and disulphide of carbon takes place so rapidly, and with such facility, that ever since for the first time I observed this phenomenon, I have used the disulphide of carbon as a reagent for the detection of the phosphorus-bases; for trimethylphosphine exhibits a deportment per- fectly similar to that of the ethyl-body. The minutest quantities of these bases may thus be readily and safely recognized. The reaction is best observed by pouring the liquid to be examined upon a watch-glass, and allowing the vapour of the disulphide of carbon to flow from an inclined bottle upon the liquid. Immediately the watch-glass is coated with a beautiful net-work of the red crystals. It requires scarcely to be men- tioned that the crystals are not formed when the phosphorus-bases are combined with acids. They appear, however, readily on adding to a mixture of their salts and disulphide of carbon, a drop of potash, which liberates the bases. On the other hand, triethylphosphine may be employed with the greatest advantage as a test for disulphide of carbon. There is, in fact, no test for this substance, which in delicacy could be compared with it. By its aid the presence of the disulphide in the most volatile fractions of coal-tar-benzol is readily proved; even the exceedingly small quantity of disulphide of carbon diffused in the most carefully purified coal-gas may, as I have shown already in another place*, be recognized without any difficulty. When the gas is passed through a bulb-apparatus containing ether to which a few drops of triethylphosphine are added, the liquid soon assumes a reddish tint, which gradually increases in intensity, until, when the ether is evaporated, the interior of the apparatus appears coated with a delicate efflorescence of the red crystals. Scarcely more than half a cubic foot of the present London coal-gas is required for this experiment. In order to satisfy myself that disulphide of carbon may be employed with safety as a test for the phosphorus-bases, it was necessary to examine the deportment of this com- pound with the arsines and stibines. Disulphide of carbon exhibits no reaction with tri- ethylarsine and triethylstibine. I have left mixtures of these bases with the disulphide in contact for a considerable length of time, both at the common temperature and at 100°, without being able to observe the slightest alteration. I have also satisfied myself that disulphide of carbon, at all events at the common temperature, is without action upon phosphoretted hydrogen. * Quarterly Journal of the Chemical Society, vol. xiii. p. 87.