The bones, crushed small, are to be boiled for 15 minutes in a kettle of water, and the fat (which is fit for all common purposes) skimmed off as soon as cold. The bones are then to be ground, and boiled in 8 to 10 times their weight of water (of which that already used must form a part), until half of it is wasted, when a very nutritious jelly will be obtained. Iron vessels should alone be used in this process, as the jelly and soup act upon copper, brass, and the other common metals. The bones of fresh meat are the most productive; those of boiled meat come next, whilst those of roasted meat scarcely afford any jelly. As ‘boning’ meat before cooking is now a very general practice, a quantity of fresh bones may always be obtained.
Bones are, for the most part, WROUGHT, TURNED, BLEACHED, and DYED in a similar manner to ivory, but with less care, owing to their inexpensive and coarser character. Before being submitted to any of these operations they are, however, first submitted to long boiling, to deprive them of grease.
The bones of living animals may be dyed by mixing madder with their food. The bones of young pigeons may thus be tinged of a rose colour in 24 hours, and of a deep scarlet in 3 days; but the bones of adult animals take a fortnight to acquire even a rose colour. The bones nearest the heart become tinged the soonest. In the same way extract of logwood tinges the bones of young pigeons purple. See Bleaching, Dyeing, Ivory, &c.
In all manufacturing processes in which bones are operated upon, foul vapours, unless special precautions are observed, will be thrown off, to the great annoyance and discomfort of those living near the building where the operations are performed.
To avoid this the offensive vapours should always be carried by a flue made for the purpose into the furnace-fire, and there consumed. But this will not remedy another source of annoyance which arises from the disgusting stench caused by the putrefaction of the flesh adhering to the bones, which lie in heaps about the premises.
The trade of a bone-boiler comes under the head of offensive trades (see ‘Public Health Acts,’ s. 112-114), and is under the control and regulation of an urban sanitary authority, which has also the power of preventing the bone-boiling being carried on within its district if it thinks proper.
BONE′-ASH. Impure triphosphate of calcium, obtained by calcining bones to whiteness, and reducing the ash to fine powder. Used to make pure phosphate of calcium, to form cupels, &c.; also sold for burnt hartshorn.
BONE′-DUST. Syn. Bone-manure. Bones (previously boiled for their grease) ground to different degrees of coarseness, in a mill. It is sown along with the seed in a drill. Wheat thus treated is said to yield 30 to 50 per cent, more weight in straw and grain than by the common methods. Turnip and other light soils it renders more than ordinarily productive. Bone manure is much used in the west of Yorkshire, Holderness, and Lincolnshire. The usual quantity per acre is 70 bushels, when used alone; but when mixed with ashes or other common manure, 30 bushels per acre is said to be enough. When coarse, and applied in the same manner as other manures, it has been found to remain upwards of seven years in the ground, the productiveness of which it has increased during the whole time.
BONE′-GLUE. See Gelatin.
BONE′-GREASE. From refuse bones, bruised, boiled in water, and the broth skimmed when cold. Prod. 1⁄8th to 1⁄4th of the weight of the dry bones. (Proust.) Used for making soap and candles. See Charcoal, Animal.