I purposely avoided filtering the solution of caseïn in carbonate of soda, because a concentrated solution passes very slowly through the filter, because caseïn in solution in the alkalis is easily altered; and because saturation by an acid precipitates caseïn in very dilute solution, not in the state of a coherent mass, but under the form of finely divided flocks, but which can be separated from it only by filtration, and then it is very difficult to avoid alteration by the filaments of the paper. Casein, thus obtained, still contains sulphuric acid; when it is put in contact with the water, this acid renders it partially soluble, especially at a high temperature. This solution forms on its surface, by evaporation, a transparent pellicle which is renewed after it has been removed. If we add to this liquor a solution of carbonate of soda, the caseïn, held in solution by sulphuric acid. is precipitated in voluminous white flocks, which are redissolved in the least excess of the precipitant. After having removed a considerable portion of the acid by washing with water at the ordinary temperature, from sixty to seventy times its weight of pure water is poured on the caseïn, in a capsule, and it is heated to ebullition; it is then left to repose. After it has deposited, the super-natant liquor is decanted, and this operation is repeated with a fresh quantity of pure water. By this process no loss of substance is experienced, since, by the addition of a small quantity of carbonate of soda, all the casein contained in the washing waters, may be precipitated from its combination with sulphuric acid, and may be obtained in the state of purity by washing it with water, alcohol, and ether. After fifteen or twenty repetitions of the treatment of caseïn by water, in the manner above indicated, this substance lost, with the acid which it contained, the property of dissolving in water; this liquid could then dissolve only small quantities of it. In order to remove the last portions of fatty matter which the casein might still retain, at the same time as the water which swelled it up, it was submitted to ebullition with absolute alcohol, and then with anhydrous ether, until these liquids gave no residue by evaporation. To convince myself of the absence of sulphuric acid in the casein obtained in this manner, I dissolved it in carbonate of potassa. I evaporated the solution to dryness, and I heated the product in a close vessel until the casein was completely destroyed; I poured on the residue water acidulated with a small quantity of hydrochloric acid, and after the disengagement of sulphuretted hydrogen, I added a solution of chloride of barium, and sulphate of baryta was not formed. I made a second experiment with the same object; caseïn, arising from the same preparation, was dissolved in carbonate of soda and submitted to ebullition; the solu. tion was decomposed by hydrochloric acid, and filtered. I added chloride of barium to the filtered liquid, without sulphate of baryta being formed. As these experiments proved the absence of sulphuric acid in pure caseïn, extracted by that acid from its solution in carbonate of soda, it might be expected that it would no longer retain any traces of the other acids used in precipitating it from its solu tion in the alkalis. In order to demonstrate it by experiments, caseïn, obtained in the manner above indicated, was dissolved in carbonate of soda, precipitated from this solution by acetic acid, and then heated by the process indicated for that which had been precipitated by sulphuric acid. The casein thus obtained, treated by alcohol and ether, had absolutely the same properties as the casein precipitated by sulphuric acid. Moistened by concentrated sulphuric acid, it did not give any odor of acetic acid. It was, moreover, impossible to demonstrate the presence of this acid in the water, which was deposited against the sides of a cooled glass vessel held over a heated mixture of casein and dilute sulphuric acid. Mulder already indicated that the precipitate produced in milk, by acetic acid, does not contain that acid. Now, as casein, precipitated from its solution in carbonate of soda, by sulphuric and acetic acids, does not contain any traces of these acids, it results that these acids precipitate caseïn from its solution in the alkalis, not in the state of combination with the acids employed in the decomposition, but pure and free from acids; it is precipitated in this latter state on account of its sparing solubility in water, as soon as the acids are combined with the bodies to which its solubility is due. In this case caseïn, by whatever acid it may be precipitated, should present the same composition. Casein precipitated by sulphuric acid should not present less carbon and hydrogen than that precipitated by acetic acid. The analyses of caseïn obtained in different manuers confirm this supposition. 1. 0:3265 of casein precipitated by sulphuric acid and purified in the manner above described gave 06445 of carbonic acid and 0.2090 of water. 54.27 II. 53.93 .. III. 54.19 Carbon Hydrogen 7.11 .. 7.07 .. 7.17 0-4604 of caseïn employed in analysis I., and which had served for the preparation of the products whose analyses are mentioned under the numbers II. and III., left, by combustion, 0·0015 of ashes; that is, 0.3 per cent. These analyses, which completely agreed with one another, give a rather higher proportion of carbon than the average numbers deduced by Dumas from his numerous analyses. This difference may be explained by that of the modes of desiccation employed by Dumas and myself. I dried the substance at 261° F., whilst Dumas dried it in vacuo at 252° F. In order to ascertain that there is no other reason for the difference, I heated for three days at 212° F. casein arising from the same preparation as that employed in analysis I., and then I calcined it. It had then kept its white color, whilst the caseïn dried in the oil-bath had acquired a yellowish tint. 0.7055 of casein dried at 212° F. yielded by combustion (which I operated like the preceding with chromate of lead) 1·36 of carbonic acid, which is equal to 53-33 of carbon per cent. The difference is owing, therefore, to the different mode of drying. Casein, obtained by one of the foregoing processes, is very sparingly soluble in water. Some casein was left for three hours in contact with water at a temperature near ebullition, and it was afterwards boiled for half an hour; 18.989 of the cooled and filtered solution then left a residue of only 0.0045 of casein after evaporation in the sand-bath and desiccation at 252° F., which is equal to 0-237 parts of casein to 100 of water. Whether precipitated from its solution in the alkalis by an acid, or from its solution in acids by carbonate of soda, casein always possesses the property of reddening litmus paper, and retains it even after desiccation at 261° F., without communicating it to the water with which it it is boiled. This re-action agrees very well with the property possessed by casein of forming neutral liquors with the solutions of alkaline carbonates; it also accords with that of causing the alkaline re-action of phosphate of soda to disappear. This salt, in solution in water, dissolves a very great quantity of casein, and forms with it a mucilaginous frothy liquor, which it is impossible to obtain perfectly clear by filtration, and which, after evaporation in a sand-bath, leaves the combination of casein and phosphate of soda, under the form of a nitreous pellicle, detaching itself from the sides of the vessel. 20:5327 of a solution of casein in phosphate of soda, which had been diluted with a very great quantity of water, and which was left for several days at the ordinary temperature in contact with a great excess of casein, after evaporation in the sand-bath and desiccation at 212° F., left a residue of 0·1098, which answers for 100 parts of water to 0.5349 parts of the combination of caseïn with phosphate of soda. Notwithstanding the acid re-action, caseïn, put in contact with bicarbonate of potassa, does not expel carbonic acid at the ordinary temperature. The substance is dissolved with facility and in considerable quantity in the carbonated and caustic alkalis, and is precipitated from these solutions by all the acids except carbonic acid. The precipitate is re-dissolved in a great excess of acid. The solutions of casein in the dilute acids are turbid, cannot be obtained clear by filtration, froth by agitation, like solutions of soap, and by evaporation are covered with a transparent pellicle, which is renewed after it is removed. If to a solution of casein in an acid another of a salt of baryta be added, turbidness is produced by the formation of an insoluble combination of caseïn with baryta, even when the quantity of casein is very small. From the foregoing investigations it results that pure casein is almost completely insoluble in water; that the so-called soluble casein is a combination of caseïn with potassa, soda, or lime; that the coagulation soluble of casein by the acids consists only in the combination of acid with the potassa soda, or lime of the combination; the casein separated from the liquor can then no longer remain in solution, being insoluble as it is in water; but it precipitates (coagulates). These investigations demonstrate, besides, the reason why the solutions of potassa are endowed with the property of opposing coagulation when added in very small quantity to milk, and also give an explanation of the coagulation of milk by slight causes, especially in the warm summer months. It is only necessary for an infinitely small quantity of lactic acid relative to the mass of the milk, to be formed, to saturate the very small proportion of soda which is sufficient to hold in solution an enormous mass of caseïn. DR. URE'S "REVENUE IN DANGER I SEND you the following remarks on Dr. Faraday. I myself have heard Liebig and others say, "that Graham, as a chemist, holds the first rank in Britain." What has Dr. Ure done for the science of chemistry? His "Dictionary on the Arts and Manufactures" is chiefly compiled from German authors. As it is perfectly well known that Mr. Brande committed the same mistake, why did not the Doctor also include him in his censures? Is it, as it is whispered, that he is casting a sheep's eye on the chair of the Royal Institution? or, what is far more likely and more interesting, on the Mint? Having so far censured, let us now praise; "it is certainly the best specimen of Uric acid that has ever fallen under my observa. tion." These remarks have only just reached me from the University of Giessen, for they were penned almost immediately on the publication of Dr. Ure's pamphlet, which roused the indignation of those who hold Mr. Graham's talents in high estimation. I am, Gentlemen, Respectfully yours, A CHEMICAL Student. In this pamphlet Dr. Ure vainly endeavors to injure the high reputation of Graham, which ranks him amongst the most scientific chemists of the present day. "Sed, risum teneatis amici," he has the absurdity to assert that he may be a better chemist than the Professor of the London University. The scientific world foolishly thinks otherwise, but it is mistaken, for it is evident in such a case the doctor himself is the best judge. For once in his long life he happens to be right by chance, and, blushing to find it fame, pens thirty-six pages to prove what no person ever doubted; for if the fluid erro-read it, however, and were much struck with neously termed naphtha had been sent to the laboratory in Giessen (along with Dr. Ure's pamphlet), thirty of the fifty students there would have ascertained its true con- [At the period of the publication of Dr. Ure's pamphlet, we purposely abstained from taking any notice of the subject of it. We the malicious spirit that pervaded the production. In our opinion, Professor Graham has little cause to be angry with the Doctor's expressions; if he regarded them, or the quarter from which they emanated, we are much mistaken. Mr. Graham's reputation is so firmly fixed, and on so high a basis, as to defy the spite and malice of even more formidable assailants than the Chemist to the Customs. With regard to the matter and manner of dispute between the Doctor and Professors Graham and Brande, we will only observe that in a similar case we should have acted very differently towards gentlemen and professional brethren. The whole pamphlet evinces a desire to profit by the occasion. We recommend the Doctor, when next he endeavors to extract the beam from the eye of another, previously to disencumber his own of the mote.] II. CHEMICAL MANUFACTURES AND AGRICULTURAL CHEMISTRY. THE SMOKE NUISANCE. A FEW remarks on this subject appear particularly called for at the present time, when legislative interference is likely soon to be interposed to suppress the nuisance, and while much difference of opinion exists among manufacturers as to the best means to be adopted for preventing the emission of smoke from their factory chimneys. For upwards of 20 years many plans have from time to time been suggested for the combustion or prevention of smoke, but with what success we are left to judge from the fact that none of them singly, or any combination of them, has been generally adopted. What we therefore propose is to to examine into the probable cause of this extensive failure of the numerous ingenious plans proposed for "smoke burning," and to suggest what appears to us the only sure method of effectually, and economically, securing the great benefit to be derived from an improved method of constructing furnaces to secure the perfect combustion of the fuel, whether of its solid portion, or of its aeriform or gaseous products. The "smoke burning furnaces" provide, in fact, for burning the largest quantity of fuel with the smallest quantity of air, than which nothing is more opposed to the simplest of chemical facts, viz., the large quantity of air required by the gaseous products of the coal. The second division of the methods under consideration provides for the admission of air to the gases of the fuel, whether olefiant gas, carburetted hydrogen gas, or carbonic oxide. These methods may be said to have little to do with the furnace itself; the grate, ash-pit, flame bed, flues, &c., remain unaltered, and what is chiefly attended to is the admission of air. These plans may be designated the chemical processes, the others being entirely mechanical, and opposing, rather than favoring, chemical views. Air may be employed either hot or cold. Many methods have been used to heat the air, as by hollow bars, dead-plates, and by coils of pipe placed in the chimney as used by Mr. Coad, or by a series of vertical pipes -an improvement on Mr. Coad's plan, patented by Mr. Samuel Hall. Two difficulties occur through heating the air: 1st, that of obtaining sufficient air in the furnace; and, 2nd, every measure of heated air contains less oxygen than air of atmos All the plans devised for burning coal without the emission of smoke from the chimney top, are, 1st, dependent on mechanical arrangements, without any consideration for the nature of the fuel, or its result-pheric temperature; and it being the oxygen ing products; or, are, 2nd, mechanical arrangements calculated to favor certain well known chemical conditions. To the first class belong all those patented furnaces called "smoke burners," for-as Watt described the process-" passing the smoke over, through, or among red hot fuel." Some of these inventions provide double grates, others revolving grates, some have an endless chain of bars, &c., &c.; another kind takes the smoke from the chimney by means of a fan and blows it into a closed ash-pit, whence it passes through the incandescent fuel on the grate. All these methods literally provide for burning smoke, and the patentees have put on record in their specifications their ignorance of the chemistry of combustion, by claiming only to purifying the smoky vapor of its blackness by the action of heat, instead of first ascertaining its origin, and then endeavoring to prevent the very formation of smoke. alone that we require for promoting the combustion of the gas. Of the hot air plans we hear of very few being in use, and they only partially answer, where the coal is not bituminous. Mr. J. Parkes, about 20 years back, admitted air through a double bridge, by which it entered in one sheet or stream of the full width of the furnace; but to this method there were many practical objections. Another, and a highly ingenious plan is that of Mr. Charles Wye Williams, manager of the City of Dublin Steam Packet Company. It consists in the direct admission of air to the coal and other gases, in the form of small films or jets. The apparatus for throwing in the air is placed in front, at the sides, at the top of the furnace, or behind the bridge, as circumstances require, the patentee having stated in his claim that he does not confine himself to the particular number, situation, or dimension of the several parts of the air distributing apparatus. Mr. Williams is the author of an elaborate treatise on the Combustion of Coal chemically and practically considered, which manufacturers desirous of obtaining information on this important subject will do well to peruse. What has been long well known in laboratory experiments, Mr. Williams has very ably and ingeniously applied on the large scale of the furnace. It is a plain and simple fact that every fresh charge of fuel is attended with a sudden and large evolution of crude coal gas requiring air in the proportion of about ten measures of air to one measure of gas, or more correctly for the various gases as follows: ...... H3 C6 H2 C O C2 Bicarburetted hydrogen Carburetted hydrogen Carbonic oxide requiring to a measure of each for the first, 15 measures of air, for the second, 10 measures, and for the third, 5 measures. Mr. Williams's method is called the "Argand Furnace," and in principle it agrees precisely with the Argand oil in gas lamps. The division of the air into small streams is undoubtedly the best for obtaining the rapid and intimate admixture of the air and gas, and the admission of the air at the common temperature brings more of the atmospherical oxygen in the same space than if the air were heated, particularly when the air is admitted at the ordinary pressure, and not impelled by a fan or other blower. If we take, for example, a cubic foot of coal gas, and 10 cubic feet of air, it is almost self-evident, that, to get them mixed, we must divide one or both into small streams, otherwise we shall have imperfect combustion and a deposition of carbon, which, mixed with the usual products of combustion, would afford what is popularly called smoke, but which, having no other combustible in it than the carbon, cannot be economically consumed, though it may be scientifically and most advantage ously prevented. The attempts to consume smoke, instead of being directed to the conditions requisite for the perfect combustion of the gas have led to many serious and expensive blunders, and as no plan can be lasting which is based on incorrect principles, though it may be temporarily forced into use, and for a while deceive the unsuspecting, we have much pleasure in bearing testimony to the leading facts of the case as respects the abatement of the smoke nuisance, and may safely affirm that unless based on chemical principles no plan can be safely and satisfactorily recommended. The smoke being the result of the imperfect combustion of the impure gas, all we have to do is to provide sufficient air, in the best manner, to to obtain its perfect mixture preparatory to its ignition, and by no other method can economical combustion be conducted. THE HEALTH COMMISSION. Liverpool, Sept. 15th, 1843. To the Editors of The Chemist. GENTLEMEN, As an inhabitant of the town of Liverpool, may I be permitted, through the medium of your journal, to express my surprise at the appointment of Mr. Lyon Playfair as the Commissioner to inquire into the state of this town as regards the health of its inhabitants? I should like to know, as would many of my fellow-townsmen, the qualifications which the Government have discovered in Mr. P. to render him eligible for such an important office; if they have found these qualifications in him, they have been more fortunate than the great bulk of men: this may, perchance, be due to their greater penetration and discernment. For my own part, but with all due deference to the sagacity of Her Majesty's advisers, I consider this appointment anything but fair play towards the people of Liverpool, and an insult to their understanding. Here we have many eminent men of science, and men possessing an intimate acquaintance with the town, and why, may I ask, should they have been passed by and a person almost as great a stranger to the town as to science, selected in preference ? It may be supposed that this complaint emanates from one whose jealousies are excited; but I assure you that this is not the casc, for my risible organs were those which were most acted on when I read the whole list of Commissioners, and meditated over the respective claims of each individual. It must be evident to any mind capable of reflection, that, to fulfil the legitimate objects of such a commission, men should have been chosen and appointed to those localities with which they were absolutely intimate; men with a perfect acquaintance with the manufactures carried on in the town and its vicinity; with a knowledge of what those works discharge into the waters and into the atmosphere; in fine, possessing a thorough acquaintance with everything that pertains to the place. The fact of a man being chemist to an agricultural society, however well he may fulfil that occupation, and whatever absurd theories he may be able to create, wherewith to amuse its members, can be no proof of fitness for the office in question. Oh, when will our Governments lose |