Separation of arsenic : From the Transactions of the Society of Arts. Vol. LI. The large gold medal was presented to Mr. James Marsh, of the Royal Arsenal, Woolwich, for his method of separating small quantities of arsenic from substances with which it may have been mixed. / [By James Marsh].

  • Marsh, James.
Date:
1842
Catalogue details

Licence: Public Domain Mark

Credit: Separation of arsenic : From the Transactions of the Society of Arts. Vol. LI. The large gold medal was presented to Mr. James Marsh, of the Royal Arsenal, Woolwich, for his method of separating small quantities of arsenic from substances with which it may have been mixed. / [By James Marsh]. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

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    porter, tea, coffee, or soup, and, indeed, with all muci- laginous and albuminous mixtures. The means I adopt to prevent this effect from taking place, or, at least, for checking it in a great measure, is to grease or oil the interior of the short limb of the apparatus before intro- ducing the substance to be examined, or to put a few drops of alcohol or sweet-oil on its surface previously to introducing the stopcock and its appendages. I have, however, found, if the tube be ever so full of froth in the first instance, that, in an hour or two, if left to itself, the bubbles burst, and the interior of the tube becomes clear without at all affecting the results. In cases where only a small quantity of the matter to be examined can be obtained, I have found a great convenience in using the small glass bucket (^, fig. 2). Under such circumstances, the bent glass tube may be filled up to within an inch of the short end with common water, so as to allow room for the glass bucket., which must be attached to the cork, &c. by means of a little platina wire ; a bit or two of zinc is to be dropped into the bucket, with a small portion of the matter to be examined, and three or four drops of diluted sulphuric acid (acid 2, water 14) ; and the whole is then to be introduced into the mouth of the short limb of the tube. The production of gas under this arrangement is much slower, and, of course, requires more time to fill the tube, than in the former case; but the mode of operating is pre- cisely the same. Indeed, it is of great advantage, when the quantity of arsenic present is very minute, not to allow the hydrogen to be evolved too quickly, in order to give it time to take up the arsenic. A slender glass funnel will be found of service when as much as a table-spoonful, or even a tea-spoonful of