In conclusion, it may be remarked that the best purifiers of the skin are soap and water, followed by the use of a coarse but not a stiff cloth, in opposition to the costly and smooth diapers that are commonly employed; and the best beautifiers are health, exercise, and good temper.
Skin, Goldbeat′er’s. See Goldbeater’s skin.
SKINS (of Animals). The preparation and preservation of fur skins are noticed under Peltry; the preparation and uses of the skins of the larger animals under Leather, Tanning, Tawing,
&c.
SLACK. Small coal, such as is used for kilns.
SLAG. The semi-vitrified compounds, produced, on the large scale, during the reduction of metallic ores by fluxes. Those from iron and copper works are often used for building materials, mending roads, &c.
According to Egleston[167] the following are some of the industrial applications to which the slag from blast furnaces is put.
[167] Dingler’s ‘Polytech. Journ.,’ ‘Journ. Chem. Society.’
When required for building stones the slag is run from the blast furnace into a semicircular vessel on moving wheels, and having its bottom covered three centimetres deep with sand and coke dust. By means of a bent iron instrument the slag is mixed with sand and coke dust till the escape of gases has nearly ceased and the mass is sufficiently tough. With the same tool it is next pressed into a mould furnished with a lid, which is forced down as soon as the escape of gas ceases. The red-hot stone is then placed in the cooling oven, covered with coke dust, and allowed to remain three or four days to cool completely. These stones are impervious to damp, and make good foundations. According to another method the slag, which should contain from 38 to 44 per cent. of silica, is run down a shoot into a large cavity, and then covered over with sand and ashes, and left to cool from five to ten days, when it is distributed in moulds, and there hardens. In certain parts of Belgium slag is poured upon iron plates and cooled by water, and thus a kind of glass is manufactured.
In other districts the slag is granulated as it flows from the blast furnace by means of a stream of water. The granulated slag is preferred by the puddlers to the sand for the moulds of pig iron. The slag gravel may be advantageously substituted for sand in mortar making, a more rapid hardening being thus secured, a matter of great moment in building foundation walls.