Thirty-eighth annual report [of the] Local Government Board. Supplement in continuation of the report of the Medical Officer of the Board for 1908-09, containing Reports and papers on the nature, uses and manufacture of ferro-silicon, with special reference to possible danger arising from its transport and storage / by S. Monckton Copeman, Samuel R. Bennett and H. Wilson Hake.

Date:
1909
Catalogue details

Licence: In copyright

Credit: Thirty-eighth annual report [of the] Local Government Board. Supplement in continuation of the report of the Medical Officer of the Board for 1908-09, containing Reports and papers on the nature, uses and manufacture of ferro-silicon, with special reference to possible danger arising from its transport and storage / by S. Monckton Copeman, Samuel R. Bennett and H. Wilson Hake. Source: Wellcome Collection.

    105/162 (page 81)
    absence of phosphoretted and arseniuretted hydrogen, but to make the experiments in such a manner as to compare all the samples without prejudice to any particular manufacturer. In order to cope with this problem successfully it was clearly necessary to determine the total poisonous impurities in each of the typical samples examined. On this basis only was it possible to make a complete and entirely fair comparison. It further be- came necessary to devise some of the methods by which both the phosphoretted hydrogen and arseniuretted hydrogen could be accurately and separately determined, as especially in the case of the first-named gas no generally recognised methods have been suggested. I think, however, I have successfully overcome this difficulty. Before describing my methods, reference must be made to the fact that while the estimation of the total poisonous impurities tends to emphasise the safety of some grades of ferro-silicon, it may perhaps somewhat exaggerate the potential danger pertaining to other grades, though not invariably. To make this point clearer, it is important to consider the total poisonous impurities in connection with the tendency already referred to (see Hardness, p. 76) of certain grades to disintegrate spontaneously, and so to offer a larger surface to the action of moist air, while it must not be forgotten that other grades, though brittle and not entirely free from poisonous impurities, are yet less dangerous since they do not show this tendency. Further reference to this point will be made later in discussing the results of the quantitative estima- tions. Estimation of Phosphoretted Hydrogen.—After several attempts to oxidise the phosphoretted hydrogen by passage of the gas evolved from the samples into (1) nitric acid, (2) permanganic acid, (3) bromine water, &c., none of which methods proved satisfactory for various reasons, I finally made the following three series of experiments on a number of typical samples, approaching the estimation from three entirely different stand- points, with what, I think, may be considered a practically perfect agreement of results. The following is a description of the methods employed : — In all cases immediately before rflaking the estimations the sample was powdered and three quantities of 10 or 20 grammes weighed at once and placed in three flasks of 100 c.c. capacity, with 20 c.c. of water, and the flasks corked. Identical samples were thus secured, and the following three estimations carried out without delay. (a.) Estimation of Silver Precipitated from a Decinormal Solu- tion of Silver Nitrate by the Gas Evolved from a Known Weight of the Powdered Sample by the Action of Water. [3Ag = PH3],— One of the flasks containing the sample mixed with water, as above described, was next fitted with a cork through which a piece of thermometer tubing, bent twice at right angles, was passed, a pipette being attached to the free end of this delivery tube. The flask with cork and fitted tubes attached was then fixed over a sandbath, and the end of the pipette arranged to dip to the bottom of a conical vessel containing 10 c.c. of decinormal silver nitrate solution (Fig. 7). The sandbath was then heated and the 14308 F 2