In galvanising and tinning acid fumes, injurious acroleic vapour, and metallic fumes can arise as the metal articles (iron, copper, &c.) first require to be cleaned in an acid bath and then dipped into molten fat or molten zinc or tin. Here also the fumes should be drawn away in the manner described.
Recovery and Use of Mercury
Escape of mercury vapour and development of sulphur dioxide seriously endanger workers engaged in smelting cinnabar. The danger can be minimised by proper construction of furnaces preventing escape as far as possible of fumes and most careful condensation of the mercury in impervious and sufficiently capacious chambers and flues.
Continuous furnaces are to be preferred to those working intermittently. The system of condensing chambers and flues must offer as long a passage as possible to the fumes, and care must be taken to keep them thoroughly cool. Removal of the deposit rich in mercury from the flues is especially fraught with danger. This work should only be carried on after efficient watering by workers equipped with respirators, working suits, &c.
Use of mercury.—Mirror making by coating the glass with mercury used to be one of the most dangerous occupations. Now that a fully adequate substitute for mercury has been found in the nitrate of silver and ammonia process, use of mercury should be prohibited. As a home industry especially mirror coating with mercury should be suppressed. Fortunately the dangerous mode of production is rapidly being ousted.
The following requirements are contained in a decree of the Prussian Government dated May 18, 1889:
(1) Medical certificate on admission to employment in mirror making with use of mercury;
(2) restriction of hours to six in summer and in winter to eight daily, with a two hours’ mid-day interval;
(3) fortnightly examination of the workers;