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The bricks were slightly baked before being painted; they were then taken from the kiln, painted and enamelled on one side only, the flux and glazes used being composed of silicate of soda aided by oxide of lead; thus prepared, they were again submitted to the action of fire, care being taken to place the painted side upwards, and having been thoroughly baked were then ready for use.
1 1/4 cwt. nitrate of soda 0 17 6 1 " impure sulphate of magnesia 0 5 0 3/4 " silicate of soda 0 11 3 3/4 " common salt 0 2 0 1 1/4 " gypsum 0 2 0 Mixing and applying it, say 0 2 3 Total for statute acre L2 0 0
In open air, where they are attacked by various destructive agents, few of the rock- making minerals are stable compounds except quartz, the iron oxides, and the silicate of alumina; and so it is to one or more of these comparatively insoluble substances that most rocks are reduced by long decay. Which produces a mantle of finer waste, frost or chemical decay? which a thicker mantle?
In his time, the native carbonate and the silicate of zinc were confounded as one species under the name calamine; but his researches distinguished between the two minerals, which are now known as Smithsonite and Calamine, respectively. "To theory Smithson contributed little, if anything; but from a theoretical point of view, the tone of his writings is singularly modern.
By using sulphate of baryta, ultramarine, oxide of chrome, etc., mixed with silicate of potash, fast colors are obtained similar to the semi-transparent colors of painted windows. By this means a variety of cheap painted glass may be made. Should these colors be fired in a furnace, enameled surfaces would be produced.
This is a very different thing, and one which, if it be not carefully guarded against, will lead to nothing but disappointment. Again, the silicate of soda may be properly made, in the first instance, but in a long exposure to the atmosphere, the soda attracts carbonic acid, and is liberated from the silex, and this has disappointed my expectation more than once.
Chemistry proved that too small a quantity of silicate made John Barleycorn weak in the knee; ammonia, animal phosphates, nitrogen, and so on, were mere names to many ignorant folk. The various stages and the different developments of insect life were next to be considered. As to the soil and strata the very groundwork of a farm geology was the true guide to the proper selection of suitable seed.
All about him the fresh morning was falling; yonder shone a green-mottled face of granite, and there a red iron blow-out streaked with veins of glittering silicate, and in this corner, still misted with the last delicate shades of night, glimmered rhyolite, lavender-pink. The single-jack dropped from the hand of Gregg, and his frown relaxed.
Lapis-lazuli, for instance, was replaced by blue frit made with an admixture of silicate of copper, and this was reduced to an impalpable powder. The painters kept their colours in tiny bags, and, as required, mixed them with water containing a little gum tragacanth. They laid them on by means of a reed, or a more or less fine hair brush.
It is true we do not find oxides, carbonates, or bromides of gold in Nature, nor can we feel quite sure that gold now exists naturally as a sulphide, chloride, or silicate, though the presumption is strongly that it does. If so, the deposition of the gold may be ceaselessly progressing. Generally reef gold is finer as to size of the particles, and, as a rule, inferior in quality to alluvial.
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