As the danger from arseniuretted hydrogen gas is especially great in processes in which acid acts on metal and either one or both of them contain arsenic, the materials, should be as free from arsenic as possible, in the production, for example, of hydrogen for soldering, in extracting metals by means of acids, in galvanic elements, in accumulator works, in the storage and transport of acids in metal vessels, and in galvanising.
In any case the workers in these industries should be warned of the danger and instructed in case of emergencies. For soldering exclusive use of hydrogen produced electrolytically and procurable in steel cylinders is advisable.
Extraction and Use of Gold and Silver
In the extraction of gold and silver by amalgamation and subsequent volatilisation of mercury there is risk of mercurial poisoning. The preventive measures necessary are similar to those for poisoning in the recovery of mercury (see p. [327]).
Argyria in pearl bead blowers can be avoided by using pumps to blow the silver solution into the beads instead of the mouth.
In electroplating the possibility of poisonous fumes arising from the baths must be guarded against because hydrocyanic (prussic) acid, though only in minute quantities, may be evolved; care must be taken that the workrooms are well ventilated or the baths hooded. Careful personal hygiene is essential, for the prevention of skin diseases from which workers in electroplating often suffer.
VII
PREVENTIVE MEASURES IN OTHER TRADES
Ceramic Industry
In the glass industry use of lead, chrome, and arsenic compounds should be restricted as much as possible or allowed only under suitable precautions (exhaust ventilation, personal hygiene, &c.).
Etching on glass by means of hydrofluoric causes almost inevitably injury to the workers. Rendering the surface of glass opaque should preferably be done by sand blast. When a bath of hydrofluoric acid for etching on glass is used the fumes require to be drawn away by hoods over the baths and the work-rooms well ventilated.