42

DYEING AND CALICO PRINTING.

alkalies, or the pedtic ferment (pedtase), is converted first into pedtine, theninto pedtic acid, and other produdts in succession. It is not improbable thatthis may be the case with cotton fibre also; but as yet no experiments havebeen made to decide this point.

Pedtic, parapedtic, and metapedtic acids have recently been discovered byDivers and Abel among the produdts of the spontaneous decomposition ofgun-cotton; and the latter maintains that “ these substances have been sofrequently obtained, that they must be regarded as general produdts of thegradual decomposition of gun-cotton.” If from this we are to infer that theacids named are derived from nitro-cellulose itself, Dr. Schunck thinks it willbe granted that there is little probability in the supposition, and that it issafer to assume that these acids pre-existed in the cotton fibre, in the form ofpedtine or pedlic acid, before the adtion of nitro-sulphuric acid on it.

According to Fremy, the pedtic acid of plants is always accompanied by asmall quantity of an albuminous substance. It seemed not improbable thatthis might also be the case with the pedtic acid of cotton; but as the pre-paration in a state of purity of a body of this class when occurring along withthe other constituents of cotton fibre would without doubt have been a verydifficult task, it was determined to ascertain whether, by the adtion of causticalkalies on the impure pedtic acid of cotton, any of the produdts of decom-position of albumen could be procured, some of which are bodies of verycharacteristic properties. For this purpose a quantity of the brown precipitatethrown down by acid from an alkaline extract of cotton was exhausted asfar as possible with boiling alcohol; it was then dried, a quantity of hydrate ofsoda, equal in weight to that of the dry residue, together with a little wateradded, and the mixture heated over the fire in an iron ladle, with theprecautions which are usually observed in the preparation of leucine andtyrosine from animal matters. The decomposition was accompanied by acopious evolution of gas and a strong smell of ammonia, the latter beingprobably derived for the most part from the colouring matter present, whichhad not been completely removed by the alcohol. The disengagement ofgas having ceased, the mass was treated with boiling water, in which itdissolved almost entirely, yielding a dark brown solution. To this there wasadded an excess of acetic acid, which gave a brown flocculent precipitate.This having been filtered off, the liquid was evaporated. During evaporationit deposited a considerable quantity of a brownish-white crystalline powder,consisting of oxalate of soda. This was filtered off, purified by re-crystallisationfrom boiling water, and converted into oxalate of lead, from which there wasobtained, in the usual manner, a quantity of pure crystallised oxalic acid,weighing 18-3 grms. The mother-liquor of the oxalate of soda was evaporated.It left a dark brown syrup, which was dissolved in boiling alcohol, and mixedwith concentrated sulphuric acid as long as any sulphate of soda was pre-cipitated. The latter having been filtered off, acetate of lead was added, andthe liquid, after being filtered from the precipitated sulphate of lead, wasdeprived of its excess of lead by means of sulphuretted hydrogen, filteredagain, and evaporated. The brown syrup which remained was mixed with alarge quantity of alcohol and left to stand for several weeks. During this periodthe liquid gradually deposited a quantity of white crystalline needles, which,after being filtered off, washed, and dried, weighed o-6 grm. These crystals