monly called cat-gut, and from some trials, promised superior advantages when applied to mechanical operations.

Isinglass is also of great use in medicine, and cookery.

EXPERIMENTS ON GLUE MAKING.

To the editor of the Tradesman, or Commercial Magazine. SIR Berwick, 8th June, 1809. ON looking over the 7th Number of your Magazine, I observe a letter from Perth, with some observations on making glue. I am not so perfectly acquainted with the process of glue making as to give complete directions to any person wishing to embark in that manufactory, but making experiments on a variety of substances, which seemed likely to be converted into that article, engrossed much of my attention for some years. Some of my experiments may possibly excite a smile from the professed chemist, but at the same time I am persuaded that they may be of some use to the practical experimentalist, and may possibly save a great deal of both time and trouble to any who may be inclined to pursue the same object. My time would not admit of putting down in writing the twentieth part of my experiments, but the result of the most conspicuous is perfectly fresh in my memory.

I learn one useful lesson from your correspondent, which is, we should never be too confident, that we have collected all and every information which a town, a certain district, or journey may procure, however minute our observation and enquiries may have been; I had no idea that there was a town or village, either in the north or south, but some person knew that all sorts of animals' skins, and every kind of leather, (except such as had reVol. II. 3 G

ceived less or more of the tanning,) was easily capable of being converted into glue, or boiled down into a jelly, which is adopted to various useful purposes without going through the full process of glue making. What first engrossed my attention, was the vast quantities of scraps and parings of tanned leather thrown away from curriers' work houses, and every shoemaker's shop. What struck me was, that if any means could be fallen on to extract the tan, that all these which are at present thrown to the dunghill, might be converted to a valuable purpose.

My first experiment was to steep a quantity of small pieces of tanned leather in water, renewing it regularly before it came to a state of putrefaction, as whenever that takes place, the substance of the leather is rendered entirely unfit for the intended purpose; but while any of the tan seemed to remain in the leather, the water kept fresh a very long time: how long I continued this, I cannot exactly say, but at least six or nine months. The water at last came off perfectly clear, and the leather seemed so soft and pliable, I had some hopes my object was obtained; but when boiled after the manner of dissolving other leather, I found that in place of dissolving into a soft or pulpy-like substance, it turned hard and brittle; if the boiling was long continued, it separated into a kind of corney substance, or into small particles, but never dissolved so as to intermix with the water. My next experiment was putting the leather into a weak solution of different acids: I thought it possible that some of these might either dissolve the tan, or at least be more powerful in extracting it than pure water; this was very often repeated, and at each renewal the leather was carefully washed with water, to prevent its being in any degree corroded by the acid. The same experiment was tried with a solution of alkali, but when the operation of boiling was

again resorted to,

the

appearances were more unpromis

ing than the former. My last experiment was steeping the leather with a certain quantity of fuller's-earth; this, of all the other substances which I tried, seemed to produce the best effect. In length of time the tan appeared to be entirely taken out, and the leather seemed as soft and had nearly the same feel as when taken from the animal; but when I reverted to the boiling, although the appearances were much more favourable, the desired effect was by no means produced: what effect longer perseverance might have had, I cannot determine, for I now began to tire. My curiosity was next directed towards fish; I tried various experiments on almost every kind caught on these shores, and the result of all was nearly the same. I soon found that the skins and fins of fish are not difficult to boil into a kind of glue, and the substance was of a most adhesive and tenacious quality, but appeared to be too susceptible of the least damp, and soon became soft. The bones, if boiled for a considerable length of time, became so soft as easily to rub into a very fine white powder, but the fish itself exhibited the most curious appearances. have often examined it with a glass of great magnifying powers, and the appearance is beautiful; the whole appears one pure lucid pulpy substance. I was, at first, confident, that the whole would, with ease, dissolve into a soapy substance, if not into glue, but how different was the result? after boiling a very long time, the whole dissolves into a thready substance, and although continued for several days, there was not the smallest difference, only the quantity reduced from its original bulk, yet the water never appeared in the least thickened, and when suffered to stand at rest, the whole settled to the bottom without shewing the smallest tendency to incorporate with the water. If a solution of either pot or pearl-ashes is used, the fish will easily melt down into a soft soapy substance, and the solution is made pretty strong, the dissolved sub

I

stance will wash much the same as soft soap. I was still anxious (if possible) to fall on some method to dissolve fish without the intervention of any other substance but

I put a certain quantity into a jar, which was kept perfectly close, till the whole was completely dissolved into a fine soft soapy mass, but the smell was so intolerable, it was almost impossible to examine it with much attention. I thought this a good opportunity to try the effect of alkali in a state of solution, to destroy any infection, or to counteract putrefaction. I mixed the putrefied fish with a weak solution of pearl-ashes, when I was most agreeably surprized to find the offensive smell destroyed in a few minutes; the only flavour which the fish retained, was resembling horn, which had got a small scorch with fire, but it was no way offensive or disagreeable.

I tried numerous other experiments relative to making glue, particularly with the common rosin, by mixing it with some substance, so as to make it soluble in water. Rice affords a glue mucilage, which in a certain degree effected that purpose; from linseed I found the same, &c. But I am afraid I have already tired your readers, who may feel very little interest in these matters; but of this I am certain, the chemical experimentalist will eagerly catch at every hint which may throw some light on the effect produced by the combination of different substances, and I can assure all those who have leisure time, that no study, I had almost said no amusement, will afford so large a fund of entertainment as chemical experiments. I well know that repeated disappointments will attend the most skilful operator, and the most plausible compounds will often produce a substance very different from what is expected; but even these very disappointments produce such appearances as doubly to increase our curiosity, and only gives a greater excitement to make farther experi

ments. It likewise has this singular advantage, that while it amuses the mind, gratifies curiosity, and enlarges all the intellectual faculties, it in general gives a good deal of exercise to the body.

I am, Sir, your's, &c.

JAMES GRAHAM.

METHOD OF MANUFACTURING GLUE.

To the editor of the Tradesman, or Commercial Magazine. SIR,

I HAVE observed in your seventh number a correspondent asking for particulars on the manufacture of glue, and again in your eighth number, page 114. In your thirteenth number, for July last, are also the results of several experiments on the clippings and parings of tanned leather, and fish bones, by Mr. James Graham, of Berwick; but I think the following process of making glue, as furnished by Mr. J. Clennell, of Newcastle, about the year 1802, is the most concise and simple of any I have read, and corresponds exactly with the practical part of that manufacture, of which I have been an eye-witness for several years, in the neighbourhood of Acton, on the road to Uxbridge. I will therefore make use of Mr. C's. own words.

"The improvement (he observes) of any manufacture depends upon its easy access to men of science, and a prudential theorist can never be better employed than in attempting to reduce to regularity or to system the manufactures that may fall under his attention. In conformity to the first principle, I made some notes whilst visiting a glue manufactory, a few years ago, in Southwark, and those interwoven with the remarks on that subject, of some chymists of the first respectability, I take the liberty of sending you; at the same time I must beg of you, or your correspondents, that where they may be corrected