BON

BON ( 158 )

infeCts, chiefly marine, which belong to theextenfive chemical genus of Shell.

Bone -when firft taken from the animal ismoift and greafy to the feel, and if cylindricalit contains within its cavity a peculiar fat calledmarrow. When this is feparated and the bonecleanfed and expofed to a dry air it graduallydries, becomes more brittle and whiter, andunder thefe circumftances may be kept for agreat length of time without any further fpon-taneous change.

Bone , though to appearance quite dry andhard, is however effentially compofed of certainfoft parts , and of an earth or rather earthy faitbefides other conftituents of lefs importance,and the feparation of thefe leading componentparts is to be effected very compleatly by theproper ufe of water, the fimpleft and leaft ex-ceptionable of all chemical reagents. It haslong been known to common obfervation thatrafped bone (hartfhorn {havings for inftance)boiled in water, furnifh a good deal of clearftrong jelly, and that uncooked bones choppedin pieces and added to the other materials forfoup affift much during the boiling in givingrichriefs and thicknefs to the liquor.

By the valuable experiments of Pelletier onprocuring glue from bones, 1 and thofe ofProuft b on the extended ufe of bone for humannutriment, the analyfis by water has been car-ried to its greateft extent.

Cold water has very little aCtion on bone,except in difpofing it after a confiderable timeto a degree of putrefaction. When raw boneschopped in fmall pieces are put into fcaldingwater, the firft effeCt is to difengage a con-fiderable quantity of oil (not marrow but a fatnaturally combined with the fubftance of bone)which melts out by the heat and rifes to thefurface of the water, concreting when cold intoa fuetty mafs which readily feparates from thewater. In this way, by only a quarter of anhour’s boiling, Prouft obtained from the knuckle.and other joint bones of beef no lefs than one-fourth of their weight of this fuet, which wasfine, white, and infipid. The {hank part of thebone and the heavy flat bones yielded lefs ofthis fat.

Anatomifts alfo conftantly find this fame oilymatter fweating out of the bones of the Ikeleton,efpecially about the joint heads where the bonesare lighter and much more open in their tex-ture, and it requires long and very careful pre-paration entirely to get rid of it.

If the above chopped bones, freed from their

oil, are now ground down to a pretty fine pafte,and again boiled with about ten times their weightof water for fome hours, till nearly half thewater is wafted, the remaining liquor will beof the confiftence of thick foup, and when coldwill concrete into a fine clear yellowilh ftiffijelly, nearly about the confiftence that wouldbe produced by difiolving one ounce of glue inthirty-one ounces of water, and extremelypalatable and nutritious. At the bottom of theveflel the powdered bones are now found, muchreduced in bulk and with little cohefion whenrubbed between the fingers. The clear jelly,which fliould be poured off when hot, if furtherevaporated {lowly towards drynefs, and after-wards fully dried as in the manufacture ofGlue , affords a very firm good glue applicableto a number of purpofes.

It is to be obferved that any kind of bonehowever dry (if uncooked) yields abundance ofthis jelly by powerful boiling with water. SoPelletier obtained a pound of ftrong glue from6 pounds of button-mold {havings, and pi-pounds of glue from 50 pounds of ivory {hav-ings. Some jelly has been obtained even from'bones kept for many centuries in cemeteries,provided they have been preferved above groundand not much expofed to moifture, fo that thisconftituent part is very flow of decay.

Scarcely any boiling in open vefiels howevercan totally feparate the gelatin and perhaps theoil from the earth of bones, for in the aboveexperiments the bony pafte after repeated andlong boiling was not abfolutely dry and friableto the touch but had fomewhat of a foapy feel,and when burned {hewed fome remains of thefoft parts. But a much higher heat than theboiling point given to the water will completelyproduce this feparation, and this is to be donein Papin’s digejler, as the inventor of this in-ftrument actually found.

The gelly obtained in this way acquires how-ever fomewhat of a burnt tafte and is lefs pala-table, but the earthy refidue is now perfectlycrumbly and harfli to the fingers, and containsfcarcely any trace of gelatin or animal fat.

Another foft part ftill remains to be men-tioned. The difcovery of it we owe to Mr.Hatchett, whofe admirable experiments on thevariety of hard animal organs, ferving for fup-port, protection and covering, have formed amolt important addition to chemical phyfiology.*When frefh bone is immerfed in any acid (thedilute muriatic or nitrous are belt) a very flighteffervefcence is perceived, and it gradually

• Memoir*, tom. ii. * Journ. de Phyf. tom. 53, • Phil- Tranf. for 1799 and 1800.