Before grinding a fresh substance in a coffee-mill, it must be taken to pieces, brushed clean, and screwed up again. Fine lawn or hair sieves should be used for sifting chemicals; excellent sieves may be made with book-muslin: the cylinders may be 4 inches diameter, 3 deep; the muslin should be cut into a circular form, and hemmed round a piece of string; it may then be slipped over the drum or cylinder, and secured; or it may be pasted up and round the sides, and if above 4 inches diameter, two pieces of string may be crossed over the middle to strengthen it.
Charcoal may be made by putting some dry pieces of willow, alder, poplar, sycamore, maple, or almost any kind of wood, except the pine or turpentine tribe, into an old iron saucepan, covering them with perfectly dry sand, and setting the saucepan in the middle of a fire, to remain red hot till the wood is completely burnt through. Remove when judged sufficiently charred; and when cold, not before, pour away the sand.
Sulphur is used in the state of sublimed sulphur, sulphur sublimatum, or flowers of sulphur, and, when mixed with nitre, requires no preparation; but as it is always more or less impregnated with sulphuric acid, as is readily shown by testing it with litmus paper, it might, on coming into contact with chlorate of potash, cause spontaneous combustion. To prevent this, it is necessary to wash the sulphur. For this purpose put it into a pan, and pour upon it boiling water, in which some salts of tartar (carbonate of potash) have been dissolved; stir it well and break down all lumps. Let it stand to subside; pour off the supernatant liquor; fill up with cold water and let it stand, to again subside. Make a conical bag, fig. 33, with a piece of linen or calico, sewed at the top, round a ring or hoop of wire, or cane, or whalebone; fasten a string to it, by which to hang it up. Put the washed sulphur into it, and hang it under a water-tap; turn the water gently on, and let it drip all night; this will wash away every trace both of acid and alkali. Afterwards hang the bag up three or four days till the sulphur is dry; it may then be bottled, and kept exclusively for colours.
Oxalate of soda may be made thus—procure 3 lbs. of carbonate of soda, the common washing soda used by the laundress, not bicarbonate of soda; boil it up in a saucepan with just as little water as will suffice to dissolve it. Dissolve, in another vessel, 1 lb. of oxalic acid in boiling water, and pour it into a deep jar, capable of holding two or three quarts; a wash-hand jug will answer. Now put to this the dissolved carbonate of soda, with a table-spoon, a spoonful at a time. A violent effervescence takes place. The soda is to be slowly added till effervescence ceases. It should be tested with a strip of litmus paper, to see if the acid is perfectly neutralized.
To prepare litmus paper, dissolve 1⁄4 of an ounce of litmus in an ounce and a half of water; when thoroughly dissolved, and the water is of a dark blue colour, take some white blotting paper, and with a sash-tool or camel's-hair pencil, go over it on both sides with the litmus solution. When dry, wet some of these prepared pieces, with the brush dipped into vinegar: this will turn them red. Dry, and preserve both. They may be cut into strips, half an inch broad; the blue strips will be tests for acids; the red, for alkalies. Wet a strip of the blue, and touch it with oxalic acid, it will turn red; wet a strip of the red, or the piece just reddened, with carbonate of soda, it will turn blue.
To make sulphuret of copper, procure some thin sheet copper, about as thick as a card; cut it into pieces, and put it into a crucible, with sulphur, a layer of sulphur, and a layer of copper alternately, till full. Set the crucible in a clear fire, and keep it red hot for an hour. Remove it; when cold, break it up, and grind it in a coffee-mill. Sift it in a lawn or book-muslin sieve as fine as possible. Half-a-pound of copper and a quarter of a pound of sulphur may be employed.
There is a black sulphide or sulphuret of copper produced by passing sulphuretted hydrogen through a solution of protoxide of copper: this is useless.
For want of a coffee-mill, charcoal may be beaten in a leather bag, with a hammer.
A variety of rocket fuses will be found in the Tables; the first is as good as any, and will answer for all sizes from 3⁄8 to 12⁄8. As a rule, the fiercer fuses, containing meal powder, may be used for small rockets; but are, by no means, necessary.
A rocket, when starting, makes a roar; but this is not on account of the fierceness of the fuse, but of the extent of the surface ignited. Rocket composition, laid in a train, burns very slowly.