180 REMARKS ON THE NATURE OF CHEMICAL AFFINITY, ETC. common chemical affinity, than in the former.* It would be wrong to close these remarks without alluding to some cases where a slight chemical affinity appears to be actually given by galvanism. We say appears, for we think it even doubtful, in such cases, whether such slight affinity is correctly said to be given even in these cases. Let us take the following experiment as an example. Gold in contact with zinc was left in common water a week. The surface of the zinc was found to be slightly oxi dized, and a small portion of lime precipitated on the gold. As this precipitate, or deposit, rubbed off immediately, it could not be said to be a case in which chemical affinity was given. It was not in union with the gold, and taking the term in its general sense, chemical affinity supposes a combination in which the properties of the separate substances are more or less decidedly destroyed. There is more difficulty with respect to the oxidation of the zinc; since when some of the same portion of metal was left in the same water without the contact of gold, it preserved its brilliancy unimpaired during the week. But what was the cause of the oxidation when the zinc was in contact with gold? Under such circumstances an electric current was produced in consequence solely of the contact of the metals. This current decomposed the sulphate of lime, &c., existing in the water, and determined the sulphuric acid to the zinc, which, by the laws of ordinary affinity, was of course, under such circumstances, oxidized. I do not know whether this explanation, which makes electricity indi This argument, however, is only insisted on to a certain extent. The power of vegetable life in controlling affinities is, perhaps, as great as that of animal life in effecting the same. Plants begin the work which animals finish Plants, probably, organise water and air; or render these elements, as they were formerly called, solid. Animals do not so decidedly do this. They merely act on and assi milate matter already organised. They rather tend to preserre, than gir, vital affinities. The reason why wood is a more permanent compound than that of animal bodies, is probably not so much because it is formed by a power that more nearly resembles ordinary chemical affinity, than that which forms the structure of animals; but rather because the composition of wood is such as to resist the play of ordinary affinity better (air and water) than dead animal matter is. When the affinity of a metal for oyygen is caused by heat the metal remains oxidized, although cold. rectly, and only indirectly, the cause of oxidation, where a fluid is unable to oxidize the metals in a state of separation, and when one becomes oxidized, when they are joined, be correct. But supposing that it is not, then we should say that the electricity merely hastens, and does not cause the affinity. Zinc alone, if left long enough in water, would, we may suppose, become oxidized. In this view then, electricity, not as being electricity, but, as under the circumstances in which it is evolved, determining acid in the solution to the zinc, only hastens common chemical affinity; and on the first view only indirectly causes it. View the matter which way we will, electricity and chemical affinity appear totally distinct powers. The former merely influences the latter. But suppose even the affinity actually caused by a direct power of electricity in this case, such affinity is a mere nothing compared with ordinary chemical affinity. Zinc and gold is the strongest galvanic combination, yet the water, so far from acting briskly on the zinc, dissolves no perceptible quantity of it in a week! The more this subject is considered, the more in our opinion will it become evident that electricity merely modifies ordinary chemical affinity, and, consequently, should be classed among such agents so admirably pointed out, and commented on by Berthollet. Indeed, some of the agents mentioned by this philosopher, as heat for instance, seem to have frequently a far greater power of increasing, if not of actually causing, affinity, than has electricity. P.S. Since the above remarks were written, I find the Baron Thenard, in the last edition of his "System of Chemistry," advocates the same doctrine that is embraced in this article. As, however, the reader may probably consider that soine additional arguments are advanced in the present paper, I have thought it right not to lay it aside. Of course, where our arguments are alike the Baron has the priority. REMARKS ON THE NATURE OF CHE- HORATIO PRATER. Berthollet, as is well known, admitted the existence of such a power as che DR. BREZA'S PATENT FIRE-PROOFING COMPOSITION. * mical affinity; he only conceived it was not elective. Although this opinion seems to have been satisfactorily refuted by Professor Pfaff, it is proposed in the present place to make a few further remarks on the subject; and first we will notice Pfaff's strongest objections, and Berthollet's reply; for adjoined to the paper in question, are notes and comments by Berthollet himself. You may remove, says Pfaff, the whole of the barytes from muriate of barytes, by dropping in enough sulphuric acid. Now, the force of cohesion to which Berthollet attributes this effect, does not act till, or exist "till, the combination is made." This is certainly true: the sulphuric acid must unite with, and, consequently, show an elective affinity for, barytes, before a precipitate falls. Berthollet makes no satisfactory reply to this objection. 2dly. You cannot decompose the sulphate or muriate of an alkali by pure magnesia, says Pfaff; boil as long as you will, no free alkali is obtained. And here we may observe that heat (itself often apparently a powerful agent in producing affinity), is shown to have no effect, though assisted by an indefinite quantity. Berthollet only replies by considering this an exception to his general law. 3. Sulphuric acid instantly causes a precipitate in solution of muriate of lead; yet, says Berthollet, by boiling muriatic acid on sulphate of lead, you obtain crystals of muriate of lead. Now, it will be observed in this case, that heat is used, often itself (as we just observed) sufficient to cause combination or affinity. 4. "I have sufficiently multiplied proofs," says Berthollet, "that it is the essence of chemical action to increase in proportion to quantity."-(Statique Chemique, 1. 339). It may be replied to this, that we may admit quantity to have often great effect, and yet hold that elective affinities may exist. Considering affinity as an essential property of matter, it will, as a consequence, be inherent in every individual atom, and, consequently, must be more or less influenced by mass. The great merit of Berthollet's writings on this subject, consists in his having so well shown that elasticity, cohe *Annales de Chymic, tom 77. 181 sion, &c. &c., influence chemical affinity; and, consequently, that such affinity is not so powerful as Bergman and former chemists considered it to be. In an essay which we propose to write on what has been called vital affinity, we shall probably turn this consideration to some account. Certainly to Berthollet science is deeply indebted; but his philosophical mind led him in this case to simplify too much. Cohesion is a species of affinity; and often much stronger than chemical elective affinity. Whether cohesion be in its nature similar to the attraction of gravitation, might afford an interesting subject for inquiry. Elective affinity is perhaps, properly considered, only a modification of the power of cohesion. Instead of combining between themselves, the particles of matter in this case tend to combine with some of opposite, or different characters. Cohesion and elective affinity seem, however, to be two essential properties of matter, perfectly distinct, though, in the respect just mentioned, bearing some resemblance. DE BREZA'S PATENT FIRE-PROOFING COMPOSITION. A patent was last year granted to a gentleman of the name of De Breza, for his invention of a new composition for rendering cotton or woollen cloths, paper, wood, and other articles, uninflammable. We now publish an account of his process, abridged from the specification of his patent. For Fireproofing undressed and unbleached goods.In two pints and a half of water, heated to 190 degrees of Fahrenheit, throw one ounce of alum, one ounce and a half of sulphate of ammonia, half an ounce of boracic acid, one drachm of animal glue, the clearest you can get, and at last one drachm of starch diluted in a small quantity of water. Care must be taken that every one of those products is dissolved separately in the above described order, and not one before the other; and previously to putting in the starch, the heat is to be raised to at least 212 degrees Fahrenheit. The goods are then dipped slowly into the solution, and, when well saturated, they are pressed or wrung to eject any redundance, and are then dried at the temperature most suitable. 182 ASTRONOMICAL QUESTION ANSWERED. For printed and dyed goods, the solution is prepared as above stated; the temperature of it is, however, only 140 degrees. The goods are to be spread on a table, and a sponge, dipped into the solution, passed over them, taking care not to put on too much of the solution for fear of taking away the colour. If the goods are fast colours, dip them in the way already described. Finish the operation as in the first process. For cannon cartridges very close calico may be used for making these articles; to the mixture already described, add half an ounce more of alum, and half anm ounce more of boracic acid, and employ half an ounce less of sulphate of ammonia. When the calico has been prepared with this mixture, and dried, cover it with a light coat of carbonate of lime and of animal glue, a composition similar to that used for whitewashing. For paper and pasteboard the compound is the same as already stated, except that double the quantity of alum and of boracic acid is used, and only onehalf that of the sulphate of ammonia, which in every case must be well purified from all excess of acid. If the paper or pasteboard are already manufactured dip them in the compound, and end the process as mentioned for the other articles. But if the paper or pasteboard are still in an incomplete or pulpy state, mix the compound with the pulp prepared for the making of paper or pasteboard, and their fabrication is finished in the usual way. For the canvas of theatre sceneries the compound is as follows:-Two pints and a half of water, two ounces of alum, two ounces of sulphate of ammonia, one ounce of boracic acid, half an ounce of glue, and four drachms of starch, which are prepared and apply as stated before; but if the sceneries are already painted and in use, paste on their inside, or wrong side, some of the paper prepared as described. Every kind of wood and timber may be rendered fireproof by immersing them in the solution. The wood or timber must at least remain 24 hours in the solution and be entirely covered by it; and it is to be borne in mind, that the time which they are to remain immersed depends on the bulk and on the quality of the wood; the hard dense woods requiring more immersion than the more tender and porous ones, and in every case ASTRONOMICALQUESTION ANSWERED. Sir, I did not intend to have noticed any proposition from Iver McIver, on account of his having so uncourteously, suffered a question, that I proposed, specifically to him, at page 69, vol. xxix, to remain unanswered. Had he answered that question, he must have, at the same time, unavoidably admitted his previous want of comprehension; but, to such an extent, it appears, his moral courage could not stretch. I shall, however, forget such want of candour, and proceed to explain the rationale of his question at page 139 of your present vol. To enable the sun to rise, or set, simultaneously to any two places, he must, at that moment, be in the pole of a great circle passing through those places. If the places be under the same meridian, he must, consequently, be in the equinox; but if they be not under the same meridian, then his declination, north, or south, must be equal to the angular distance of such great circle from a meridian. E D B To discover such declination, is a matter of very simple trigonometrical calculation. Let P, be the pole; S, the sun's place; CD, the equator; PE, PC, two meridians; and A, B, two places on the great circle C A B. In the triangle AB P, the sides A P, BP, are the respective co-latitudes of those places; and the contained angle P, is their dif NEW SOLAR SYSTEM. ference of longitude: hence the angle at A is known. And in the right-angled triangle A EC, the side A E, being the latitude of A; and the angle at A North South when the sun 183 being known; the angle at C is found, and consequently the declination required. This declination will berises To two places of which the northern is to the sets. west. There is, however, another condition essential to the proper fulfilment of the phenomenon. Not only must the sun be in the required declination on any day, but also at the very moment of sun rise, or sun set, on that day; and this would be a coincidence so extremely improbable, that its absolute fulfilment, except in theory, is next to impossible. For the places named in the question at page 139, viz. Greenwich and Edinburgh (the correct difference of longitude being 3°. 11'); the declination of the sun at the moment of rising should be 13°. 14'. 53" north: and the time, 4h. 51m. 11. A.M., Greenwich appt. time, not taking refraction into account. To conclude, I beg to propose as a question-what are the situations of two A NEW SOLAR SYSTEM. Sir,-In addressing you on this subject, I consider that I am addressing a scrutinizer for an enquiring multitude. From a thorough examination by those who are fully possessed of infinite nicety of judgement, in many matters of importance to the enquiring world, it has always been held out that the attraction of one body towards another, is in a ratio, according to their qualities, and distances; consequently, if any body has by its superabundant quantity attracted any other of a smaller quantity, 20-17" in the year 1839, and that continued attraction constantly be kept up, its force must be accelerated proportionably to the time of its nearer approach, equal to the continued square, of its nearer motion, to that. A body that moved 20-17" in time, or 50" of a degree in motion in 1839, would move more than 60' 52" in time, and 2°-30' in motion in 1840, and in 1841 increase in the same ratio; and this reasoning brought into my consideration the precession of the equinoxes; the cause of the difference between the tropical and the sidereal year. And if the attraction of redundancy of matter accumulated at the equator is the cause, as is doubtfully substantiated by all our previous astronomers and natural philosophers, how is it they do not follow the order laid down in respect to the increased ratio of attraction, by squaring the time and motion by the decrease of the distance, which according to the increased power of attraction, would bring the axis of the equator into the present position of the axis of the ecliptic, much sooner than the period allotted; and the axis of the equinoctial much farther from the north star than it is at present. Now as it has been already and ably demonstrated, that the whole of the heavenly bodies are held up, and their motions sustained by one another's attraction, and by their proportional gravitating on their common centres, so as to move according to their quantities after the projectile force was given, pray, why did not the sun receive that projectile force as well as the other bodies? I say, that if our earth was subject to the power of attraction by the sun and moon in consequence of the redundance of matter |