the alkali has. The letting loofe thefe volatile principles feems to be the beginning of putrefaction. If this be the cafe we may fee the reason why fleth, when growing putrid, is reftored to Tweetness by fixed air; that acid replacing what has efcaped, and retaining the volatile alkali. It is probably on this account, that the aerial acid is found to be of use in ftopping the progrefs of fome putrid diforders; it seems to act as a fort of pickle. If vinegar preserve flesh by keeping its volatile alkali united with this acid, which is not volatile, we may expect a fixed alkali will have a like effect in preferving flesh, by expelling the weaker volatile alkali, and uniting itself to the volatile acid, which will therefore be attained. This I found to be really the cafe; for, while the flesh and alkali were combining in the mortar, a very strong fmell arofe, like that of fal volatile; and, at one time that. I used a brafs or metal mortar, I perceived its edges to be tinged with blue, which thewed that the metal had been affected by the volatile alkali.

There feems to be a good reafon why fixed alkaline falts fhould preferve flesh much longer than any fluid acid, fuch as vinegar can do; for when the alkaline falt combines with the £efh it expels what is volatile, the mafs grows hard, and it is eafily reduced to a ftate of drynefs, in which no fort of fermentation, or any inteftine motion can take place, and therefore there is nothing that can effect a change

in

this compound fubftance. Whereas, when an animal or vegetable fubftance is immerfed in vinegar, a very heterogeneous mixture is formed, which, in

Its

I. A fubftance fo remarkable and fo useful as honey, ought to have been long fince accurately analyzed by the chemists. faccharine tafte has always led them to fuppofe that it contained a large quantity of fugar; but the great question was, how to feparate the faccharine part from the mucilaginous, and other heterogeneous parts. This feparation was the principal object of my enquiry, in the experiments which I am going to give fome account.

II. The property poffeffed by charcoal, of decompofing and abforbing the mucilaginous and phlogiftic parts of various fubftances, (a difcovery which I formerly made, and of which I then gave an account,) induced me to hope that I could, by its means, obtain the object I had in view. I did indeed fucceed in depriving honey, which had previously been diffolved in a fufficient quantity of water, of that

fmell

fmell which is peculiar to it, and also of its taste and colour; but, when I evaporated the folution, by a very gentle fire, it foon acquired its former brown colour, and did not fhew any difpofition to produce regular cryftals. I therefore thought it reasonable to conclude, that this property, of recovering its original colour, either was natural to the whole fubftance of honey, or belonged exclufively to one of those conftituent parts of it upon which charcoal had no power; for when a folution of common fugar is thickened by boiling, even though it is made to boil violently, it does not contract any colour until all the aqueous parts are evaporated.

III. The honey which had been treated with charcoal, and thickened by evaporation, in the manner already defcribed, was obferved, two months after, to have a great number of fmall white lumps in it, which had the appearance of cryftals; and, foon after, the whole mass seemed to be full of them. To diftinguish accurately the nature of these fmall lumps, it was neceffary to separate them from the reft of the mafs, which was entirely coagulated, very thick and glutinous. This operation I performed tolerably well, by washing the mass with alkalized spirit of wine, without heat. I toon perceived that the fpirit diffolved the glutinous part completely, merely by fhaking the mixture; but that fluid did not feem to have any effect upon the white granulated part; fo that I fucceeded in obtaining this laft quite pure. After having feparated this faccharine granulated part from the liquor, by means of a filter, I dried it by a

gentle heat, and reduced it into powder: this powder did not attract moisture, and had a very agreeable fweet tafte.

IV. As the granulated confiftence of white honey seems to arise from the coagulation of its faccharine parts, I endeavoured to separate that part by means of the pureft fpirit of wine, and which contained the fmalleft poffible quantity of water. From twelve ounces of this fort of honey, I procured three ounces of faccharine matter. This matter ftill contained fome heterogeneous fubftances, which appear not to be foluble in fpirit of wine. To diffolve the faccharine part, I again had recourse to the pureft fpirit of wine I could procure; which I made use of by putting the mixture into a glafs matrafs, and boiling it therein for fome time.

By these means the faccharine part was entirely diffolved; while the infoluble part remained behind upon the filter, having the appearance of a greyish dirty flime. I had filtered the mixture while it was hot; after which I had poured the clear liquor into another matrafs, in which I let it ftand quiet for some days. After that time the fugar of the honey began to fix itfelf to the bottom of the veffel, in the form of little spherical knobs, ranged in lines by the fide of each other; thefe, increafing in number every day, formed at laft a folid cruft, which was as white as fnow, rather rough at the top, and which after being feparated from the liquor above it, was fo firm as to bear cutting with a knife into very thin flices. The remaining liquor, having been left quiet for fome days, let fall, in that inter

val, a fresh portion of this faccharine matter, which was exactly fimilar to that already spoken of

V. Having thus provided myfelf with a certain quantity of this kind of fugar, I tried various methods to make it take a regular cryftalized form; but in that refpect, all my trials were in vain, Whether I used the pureft fpirit of wine, or water, to diffolve this fubftance, the refult was the fame. I remarked, indeed, that the folution of it in water, which had been thickened to the confiftence of fyrup, depofited, after fome time fmall knobs on the fides of the veffel, which had the form of cauliflowers; the whole folution afterwards coagulated, and appeared like a folid, dry, white mafs, full of small cavities, which, when examined with a microfcope, feemed to be composed of very fmall long cryfials, extremely thin, and hardly vifible to the naked eye.

VI. Though this manner of cryf talyzing fufficiently diftinguithes the faccharine part of honey from common fugar, I fufpected, at firft, that this difference proceeded only from the prefence of fome heterogeneous parts, from which the honey was not fufficiently cleared; but the following experiments evidently fhewed, that these two fubftances differ from each other by properties which are very ftrongly marked.

1. If a certain quantity of limewater is added to a watery folution of the fugar of honey, it infiantly acquires a brown colour, though it was before quite limpid and colourlefs.

2. Quick lime, which I added to the watery folution of fugar of

honey, while it was upon the fire, produced a very ftrong effervefcence, and the mixture immediately became of a dark brown colour, almoft black. By continuing to add quick lime until the effervefcence ceafed, the fugar of honey was entirely decompofed; the mixture turned quite black, and emitted a fmell which was very difagreeable, and even nadfeous.

3. The dark coloured folution contains a large quantity of lime, which cannot be precipitated by means of aerated alkali, nor by an alkali rendered perfectly cauftic.

4. If vitriolic acid is made use of to precipitate this lime, it then appears in the form of gypfum; but the remainder of the liquor ftill contains a very empyreumatic acid, which feems to have a strong analogy with the malic acid of Scheele.

5. If the acid of fugar of honey is treated with nitrous acid, it is converted into acid of fugar.

6. A much more pure acid may be obtained by making ufe of a double affinity. For this purpose, it is only neceffary to boil together equal parts of honey and quick lime, in a great quantity of water, adding to this folution, which is of a brownish colour, as much charcoal-powder as may be requi fite to take away the colour entirely. The folution muft then be filtered, and to the clear liquor must be added a very saturated solution of lead in diftilled vinegar, until all precipitation has ceafed. The precipitate obtained by these means must be washed in fuch a quantity of water as will edulcorate it thoroughly; after which, as

much

much diluted vitriolic acid muft be added as may be fufficient to feparate the acid of the honey from the lead this acid may then be concentrated by evaporation.

7. If the folution of honey and quick lime is thickened by evaporation, after its brown colour is taken away by charcoal, a tranfparent mafs, of a light yellow colour, is produced, which refembles gum arabic; it has a bitter tafle, and does not grow moift by being expofed to the air.

8. The clear mafs which is produced from a mixture of the acid of honey and lime is perfectly infoluble in fpirit of wine; and it may be precipitated from its folution in water by this fpirit.

9. Cauftic fixed alkalies produce upon honey, and upon the fugar which is procured from it, the fame effect as lime. Honey, as well as its fugar, is entirely decompofed by them; and always with a very violent effervefcence. The dark coloured extractive mafs which is obtained by thefe means is completely infoluble in fpirit of wine; and, when the quantities of the two fubftances are exactly proportioned, very little tafte can be perceived in the mafs; that little is by no means alkaline, and can hardly be called faline. This proves that alkalies, as well as quick lime, may be perfectly faturated by the acid contained in honey.

10. Volatile alkali alfo decompofes honey in the fame manner, and with the fame circumftances, as other alkalies; but this decompofition takes place much more flowly, and only when heat is at the fame time made ufe of.

VII. That conftituent part of honey which is got from it by treating it with the fpirit of wine (III.)

may be diftinguished from the fugar of honey, by the following property, viz. that it cannot be reduced into a dry or folid form. It is owing to this particular part that the folution of honey fo readily contracts a brown colour; for a folution of fugar of honey, deprived of this glutinous part, may be thickened upon the fire without fuffering any alteration of colour. In other refpects, the yellow glutinous part of honey, here spoken of, fhews nearly the fame properties as the fugar of honey; and when treated with cauftic alkalies, or with quick lime, its tafte is alfo the fame.

VIII. The properties which I have above defcribed are thofe by which the fugar of honey differs effentially from common fugar. If this laft is treated like honey, it exhibits the following refults.

1. Neither quick lime nor fixed alkalies produce any decompofition in fugar; no effervefcence is obferved, nor does the 'folution fhew any change of colour.

2. Whatever quantity of fugar is added to fixed alkalies, they always preferve their caufticity; and, even if they are boiled with fugar for a confiderable time, they never appear to be united with its acid.

As quick lime, when combined with fugar, is attended with fome phænomena which appear not to have been taken notice of by any perfon, I fhall here mention them.

By evaporating this folution to drynefs, a white tenacious mafs is obtained, which has fuch an acrid and burning taste as to affect the tongue like cauftic alkalies.

3. By expofing a folution of lime and fugar to the air, after having been filtered into an open veffel, the furface becomes gradually covered with a great number of fmall cryftals; these are fucceeded by others whenever, by thaking the liquor, the, firft formed ones are made to fall to the bottom of the veffel. This formation of cryftals at the furface continues till the liquor contains no more lime; then the fugar again acquires its proper taste.

4. The fmall crystals, of which I have just spoken, very readily lofe their water of cryftalization,by being exposed to the open air; according to my experiments, I fhould confider them only as an aerated calcareous earth crystalized.

5. One of the most remarkable properties of the filtered folution of lime and fugar is, that by being made to boil, it foon grows turbid and thick; the lime then falls to the bottom of the veffel, and this precipitate is of a milk-white colour; but as foon as the folution grows cold, the lime again diffolves in it fpontaneously, and the folution becomes once more as limpid and tranfparent as it was at firft. This phænomenon (which it is rather difficult to explain) was obferved by M. de Laffone, when,

in the fame manner, he combined the neutral falt of tartar with quick lime. (See Memoirs of the Academy of Paris, 1773, page 191.)

6. Alcohol, or very highly rectified fpirit of wine, precipitates the lime from the forementioned folution.

7. Mild alkalies, by the aerial acid they contain, produce the fame effect.

8. Cauftic alkalies do not cause the smallest alteration in the folution.

IX. From what I have faid it follows, that the union which exifts between the faccharine part of honey and the oily part is much weaker than the union between the fame parts in fugar. This laft cannot be decompofed, in the humid way, except by treating it with nitrous acid; while honey and the fugar it contains, may be decompofed, not only by that acid, but alfo by mild alkalies, and by lime.

Upon the whole, there appears very little reafon to hope that we fhall ever be able to obtain honey in the form of fugar; to bring it into that form, fomething more than a mere feparation of its heterogeneous parts feems neceffary. It is indeed faid, that, in fome kinds of honey, efpecially in that from Narbonne, cryftals of fugar, completely formed, have been obferved; admitting the fact, I confider it only as an accidental circumftance.

USEFUL