liquid bolls insert the copper into it, and lower the flame so as to maintain only a gentle simmering. By means of the wire the copper can be drawn out from time to time to examine the progress of the test.
If much arsenic is present the copper will almost immediately be coated with the colour of lampblack or dark steel; if there is less arsenic, a period varying from half a minute to half an hour, which is the extreme time, will be required. If after that limit the copper is not coated all over as above, the material may be accepted. This process, however, while negatively proving the absence of poison, does not positively prove its presence, for the coating may arise from a few other ingredients present in the colouring matter, such as mercury or sulphur. As these ingredients, however, may also be injurious, it is as well to reject the wall-paper or clothing material when the coating is observed. Arsenic is used in linen glaze, and paper collars and cuffs, and, as before observed, is largely used in the preparation of aniline dyes, but if properly managed does not pass into the "finished" dye. Hence the painful and irritating effects produced by articles of dress dyed with aniline colours, are generally caused by the dyes themselves when improperly fixed. Aniline is a narcotic poison when taken internally, and a local irritant if applied to the skin, so that the dyes derived from it may participate in its poisonous qualities. Aniline colours are largely used in artificial-flower making; and M. Napias, in a paper read before the Paris Society of State
