Gum resins are partly resinous and partly mucilaginous; as lac, assafœtida, galbanum. In submitting shellac to the action of alcohol, the whole is never entirely dissolved; as the lac contains, besides the resin, a mucilage which floats about in the liquid, and renders it turbid.
Many substances which go under the name of gums in commerce, are in reality resins or gum-resins.
Native turpentine, the juice of trees of the fir tribe, of the consistency of honey, yields on distillation spirit of turpentine, called also oil of turpentine, and by painters turps; the dry mass left behind in the retort is colophony or rosin. Rosin is soluble in alcohol, and is therefore a resin; rosin and resin, however, are not synonymous; all rosin is a resin; but all resins are not rosin. Rosin has been tried in pyrotechny, but is of no use: a solution of it in spirit will bind stars; but it renders them white and smoky.
Volatile, ethereal, or essential oils are obtained from plants by distillation with water; as oil of roses, lavender, thyme, peppermint, aniseed, &c.
Fixed oils are obtained from animal fat by heat; and from seeds of plants by pressure and percussion; as, train oil, cod-liver oil; palm oil, croton, linseed, cottonseed, &c.
Oxychloride of copper, if difficult to procure, may be made by laying thin pieces of copper in a dish, and pouring upon them a mixture of half water, and half hydrochloric or muriatic acid. The next day remove them, and lay them on a board in the shade to dry. When dry, brush off the green powder which will be found on the outside, with a toothbrush, into a basin of water. After a quantity is obtained, wash it as directed for sulphur, and dry it in the bag, fig. 33. Test it with litmus paper to ascertain if free from acid.
Saw a piece of coke or charcoal in two, and on the flat surface place a few copper filings; direct upon them the flame of a lamp or candle with the blow-pipe; they will simply become red-hot. Lay a few more filings, and on them a little calomel or sal-ammoniac: now direct the flame, and a beautiful blue colour will be produced. Any of the salts of copper may be used to obtain the same effect, the chlorine gas liberated from the calomel (chloride of mercury) or from the sal-ammoniac (ammonic chloride) giving a blue colour to all preparations of copper burnt in it.
Weights for quickmatch may be made by nearly filling the brass tube with useless rusty old nails, tacks, screws, or odd bits of iron, or brass; then pouring in melted lead. If the ladle will not hold enough lead to fill it at once, it may be poured in at twice, thrice, four or more times. A tube 11⁄4 inch diameter and 6 inches long will weigh 21⁄2 lb. This will keep a great length of match tight and straight. Half-an-inch at each end of the tube should be solid lead, one to receive the screw, and one to make a firm bottom.
If at any time the basil end of a pinwheel pipe should be too small to admit the nose of the funnel, it may be enlarged by binding a gum strip round it. If pinwheels are too dry, they break in winding, from the hardness of the composition; if too damp, from the softness of the paper. As paper cannot be relied upon for being always of uniform thickness, if it be found that a pinwheel pipe is too thin, cut the strip a little broader. Discretion may be used in all cases.
Coloured lances may be primed with meal powder very slightly damped with thin lac solution. Leader pipes may, if preferred, be fastened to lances with patent short whites: they may be procured at the haberdasher's; the price of them is 2d. per oz. Push the pin through the side of the leader, down into the side of the lance; then make a triangular hole through the middle of the leader, down into the middle of the lance, turning the tool round to break the priming, and secure the leader with a gum strip. The gum strip, bent round, assumes the shape of the capital letter T. The best tool for making the holes is a steel bradawl, ground triangular and to a sharp point; another bradawl ground to a tapering point like a needle, about 3⁄4 of an inch long, may be used for making holes up the lances to receive the wires. Scissor-grinders will shape them, if you have not a grindstone; or they may be rubbed on a stone, such as used by mowers to whet their scythes. Afterwards set them sharp on a hone.