45 Mr. J. T. Cooper 011 Catechuic Acid. December 18 184F. -The President in the Chair. A Specimen of Catechuic Acid was presented by John Thomas Cooper Esq. to the Society’s Museum. Robert Kane Esq. M.D. Amos Swaisland Esq. Thomas Jen- nings Esq. Andrew Muter Eeq. James Millar Esq. and David Waldie Esq. were elected Members ; and Rllessrs. Robert Hunt and John Mercer Jun. as Associates of the Society. The following communications were then read :- COOPER ESq. XCII. Observutions 012 Catechic Acid. By JOHN THOMAS I- 4 SHORT time since I was requested to visit a tannery where the principal tanning ingredient employed was catechu and among other matters my attention was directed to a whitish substance which made its appearance on the ex- ternal surface of the leather when the tanning process was completed and the uniform appearance of this substance over the whole surface is considered by the proprietors as the test of the perfection of their process of tanning which is usually accomplished in about fourteen days.The tanning liquor is prepared by making an imperfect solution of the catechu in warm water or in the liquor that has been previously par- tially exhausted of its tannin by a former operation; the de- pilated hides in their usual state are sewn up so as to form water-tight bags into which the tanning liquid prepared as above is placed so as to completely fill them; they are then placed on floors and turned once or twice a day into every 4 4 6 Mr. J. T. Cooper on Catechuic Acid. possible position to expose the hide as equally as possible to the action and pressure of the tanning liquid and as the pro- cess of tanning advances the appearance of this white matter becomes more and more evident until at length it covers the entire surface of the leather and sometimes acquires consi- derable thickness and solidity.In this state however it is contaminated with many impurities and after repeated trials to obtain it in a state fit for examination I found the follow- ing simple method to answer the purpose 1,had in view very well. The matter as obtained by scraping from the surface of the leather was thrown on a filter of linen cloth and washed with cold water until the water passed through very nearly colourless; by this means a quantity of tannin mucilage ex- tractive matter and a peculiar substance which I have not yet examined were removed; the matter remaining on the filter was then treated with hot water either by washing it on the filter or which is better by removal into a basin and heating it with three times its bulk of water to near the boil- ing point when a brown-coloured solution was obtained and by filtering this while hot in a warm place the substance which has the characters of catechuic acid catechine or tanningenic acid is deposited as it cools but the deposition of the whole I find does not take place until many hours after it has become cold therefore after c? lapse of about twenty-four hours it may be thrown on a filter and washed with cold water in which it is nearly insoluble until the water passes through colour- less or very nearly so and then dried slowly by exposure to a gentle heat; i n this manner the specimen herewith presented to the Society has been prepared arid which if examined will be found to possess the properties described as appertaining to catechine catechuic or tanningenic acids namely a white substance with a light tint of reddish-brown a glistening or micaceous aspect when diffused in water meagre to the feel something like alumina insolubility in cold water and ready solubility to a great extent in hot water; forming a brown solution of greater or less intensity in proportion to the quan- tity dissolved; readily soluble in alcohol and ether and in the weakest alkaline solutions without the assistance of heat tbrming brown compounds; and with the assistance of heat becoming dark brown or almost black owing it is said to the absorption of oxygen from the atmosphere and its con- version into what is called jayonic acid fusible per se into a resinous looking substance hy the cautious application of heat and if heated much beyond its fusing point becorning charred leaving a very bulky charcoal.If it be considered desirable to undertake the organic am- Catechu. 62.8 Tannin . 12-3 Water. 8.2 Extractive or colouring matter. 2- Resinous matter. 8 ' 5 Mucilaginous or gummy matter. 4.4 Insoluble matter. CutcA. Mr. Warington on tile Molecular Structure of Silver. 47 lysis of this substance in all probability the specimen presented may require further purification and by adopting the process recommended by Svanberg namely forming it into a cate- chuate of lead and decomposing this by sulphuretted hydro- gen while warm may in the hands of others be effectual for the purpose but I confess it has not succeeded well with me.- 98.2 12.8 Water. Tannin f 4 ' *ri tannin. 47.7 6*2 altered tannin. 9.2 Extract Eveor colouring matter. 13% Mucilaginous or gummy matter. 6.8 Resinous matter. 9.4 Insoluble matter. - 99.5 Mr. J. T. Cooper 011 Catechuic Acid. 45 December 18 184F. -The President in the Chair. A Specimen of Catechuic Acid was presented by John Thomas Cooper Esq. to the Society’s Museum. Robert Kane Esq. M.D. Amos Swaisland Esq. Thomas Jen-nings Esq.Andrew Muter Eeq. James Millar Esq. and David Waldie Esq. were elected Members ; and Rllessrs. Robert Hunt and John Mercer Jun. as Associates of the Society. The following communications were then read :-XCII. Observutions 012 Catechic Acid. By JOHN THOMAS 4 SHORT time since I was requested to visit a tannery I- where the principal tanning ingredient employed was catechu and among other matters my attention was directed to a whitish substance which made its appearance on the ex-ternal surface of the leather when the tanning process was completed and the uniform appearance of this substance over the whole surface is considered by the proprietors as the test of the perfection of their process of tanning which is usually accomplished in about fourteen days.The tanning liquor is prepared by making an imperfect solution of the catechu in warm water or in the liquor that has been previously par-tially exhausted of its tannin by a former operation; the de-pilated hides in their usual state are sewn up so as to form water-tight bags into which the tanning liquid prepared as above is placed so as to completely fill them; they are then placed on floors and turned once or twice a day into every COOPER ESq 4 4 6 Mr. J. T. Cooper on Catechuic Acid. possible position to expose the hide as equally as possible to the action and pressure of the tanning liquid and as the pro-cess of tanning advances the appearance of this white matter becomes more and more evident until at length it covers the entire surface of the leather and sometimes acquires consi-derable thickness and solidity.In this state however it is contaminated with many impurities and after repeated trials to obtain it in a state fit for examination I found the follow-ing simple method to answer the purpose 1,had in view very well. The matter as obtained by scraping from the surface of the leather was thrown on a filter of linen cloth and washed with cold water until the water passed through very nearly colourless; by this means a quantity of tannin mucilage ex-tractive matter and a peculiar substance which I have not yet examined were removed; the matter remaining on the filter was then treated with hot water either by washing it on the filter or which is better by removal into a basin and heating it with three times its bulk of water to near the boil-ing point when a brown-coloured solution was obtained and by filtering this while hot in a warm place the substance which has the characters of catechuic acid catechine or tanningenic acid is deposited as it cools but the deposition of the whole I find does not take place until many hours after it has become cold therefore after c? lapse of about twenty-four hours it may be thrown on a filter and washed with cold water in which it is nearly insoluble until the water passes through colour-less or very nearly so and then dried slowly by exposure to a gentle heat; i n this manner the specimen herewith presented to the Society has been prepared arid which if examined will be found to possess the properties described as appertaining to catechine catechuic or tanningenic acids namely a white substance with a light tint of reddish-brown a glistening or micaceous aspect when diffused in water meagre to the feel, something like alumina insolubility in cold water and ready solubility to a great extent in hot water; forming a brown solution of greater or less intensity in proportion to the quan-tity dissolved; readily soluble in alcohol and ether and in the weakest alkaline solutions without the assistance of heat, tbrming brown compounds; and with the assistance of heat becoming dark brown or almost black owing it is said to the absorption of oxygen from the atmosphere and its con-version into what is called jayonic acid fusible per se into a resinous looking substance hy the cautious application of heat, and if heated much beyond its fusing point becorning charred, leaving a very bulky charcoal.If it be considered desirable to undertake the organic am Mr. Warington on tile Molecular Structure of Silver. 47 lysis of this substance in all probability the specimen presented may require further purification and by adopting the process recommended by Svanberg namely forming it into a cate-chuate of lead and decomposing this by sulphuretted hydro-gen while warm may in the hands of others be effectual for the purpose but I confess it has not succeeded well with me. 12-3 62.8 8.2 2-8 ' 5 4.4 98.2 12.8 47.7 9.2 13% 6.8 9.4 99.5 --Catechu. Water. Tannin . Extractive or colouring matter. Resinous matter. Mucilaginous or gummy matter. Insoluble matter. CutcA. Water. Tannin f 4 ' *ri tannin. 6*2 altered tannin. Extract Eveor colouring matter. Mucilaginous or gummy matter. Resinous matter. Insoluble matter