true with reference to emery, many speci- the amount of silica taken from the mortar. mens of which containing the same amount The levigation of 1 grm, was accomplished of corundum differ somewhat in their effec-in two operations, each requiring about tive hardness, owing to the more or less compact structure of the corundum. By the method with the agate and glass I have found the best emery capable of wearing away about one-half its weight of the glass (that used was the common French window glass). The sapphire under the same circumstances wears away more than four-fifths of its weight. A tabular view of the results will be given a little further on. CHEMICAL COMPOSITION. twenty minutes; and by using a mortar of convenient size and the extremity of a feather or a small brush, it is possible to lose but an insensible quantity of the mineral, and to estimate with sufficient precision the amount of silica abraded from the mortar.. Another method by which I accomplished the levigation in some of the analyses, was in a steel mortar of the same form as the agate mortar; and when completed, the powder was placed in a glass with nitric This substance consisting of a mixture of acid diluted with 30 times its weight of corundum and oxide of iron in various water, and left in it for one hour, agitating proportions, it is easy to see what its com- it occasionally. The iron taken from the position must be. Yet the chemical exami-mortar was dissolved, and no part of the nation of this mineral, taken in connection mineral attacked. The next thing was to with other properties, is not devoid of interest. For the purpose of analysis, the emery was reduced to a state of powder, in the manner alluded to in speaking of its hardness, with a diamond mortar and sieve. The powder was dried for twenty-four hours over sulphuric acid; a gramme was then weighed in a small platinum crucible of about one-fourth of a cubic inch in capacity, fitted with a cover that adapted itself well to it; this small crucible was placed in another of earth, and the space between the two filled with pulverised quartz, which also covered the smaller one to the depth of half an inch. Common sand was not used, because during the heating some particles might adhere to the platinum crucible by a semifusion; nor was powdered charcoal employed, because it protected the mineral no better than the pulverised quartz from contact with the air; at the same time a little risk was run in decomposing a small amount of the iron. Thus arranged, the crucibles were heated to a bright red for from thirty minutes to one hour. After cooling, the platinum crucible was carefully withdrawn and weighed. The loss furnished me with the amount of water in the emery, It requires a continued red heat to drive out all the water, a circumstance which is true for a number of minerals, particularly for those containing a large amount of alumina, as diaspore and some micas. The powder, of which the water has been estimated, was next submitted to levigation in a large agate mortar placed on a surface of glazed paper; and when completed, it was carefully detached from the mortar, placed in a platinum capsule, heated gently to drive off any hygrometric moisture, and weighed; the increase of weight furnished filter, and continue the analysis with the substance thus freed from the iron of the mortar, without any second weighing. Of these two methods I prefer to employ the first for the emery, as it is more expeditious, and almost, if not quite, as exact as the second. There are however occasions in which the steel mortar should be resorted to. The substance once reduced to an impalpable powder, it was necessary to render it completely soluble, and my researches to arrive at this were long and tedious. In trying the various known methods, the most successful was found to be that with a mixture of carbonate of soda and caustic soda heated to whiteness for one hour; nevertheless I could not obtain a complete decomposition. The decomposition might probably be completed if the levigation was made more thoroughly; but it is easy to understand, that with a large number of analyses of the same substance to make, it was a desideratum on my part not to consume the best part of the day in the levigation of a single gramme; particularly as I did not wish to confide this operation to another, as much care was required to lose nothing during the levigation. Mixed with carbonate of baryta, and heated in a forge, the decomposition of the nineral was far from being complete; the same may be said for the treatment with the caustic alkalies in a silver crucible. The bisulphate of potassa decomposes it almost entirely by a single operation, but unfortunately a double salt of potassa and alumina is formed, which is almost insoluble in water or in the acids, and it is only by a solution of potassa that it is first decomposed, and afterwards redissolved. I will not stop to detail all the disadvantages attending this method, but will at once speak of the method which gave me very easily the most accurate results. It is by means of the bisulphate of soda that all my analyses of emery, of corundum, and of several aluminates, were made. I believe that I am the first who has shown the great advantage of using this double salt in the decomposition of certain substances insoluble in the acids; and very probably it will replace in most cases the use of the bisulphate of potassa in analytical chemistry. At present, all the advantages that may arise from the substitution of the soda for the potassa salt cannot be mentioned; all that I will say is, that the former, in giving a decomposition at least as complete as the latter, furnishes a melted mass quite soluble in water; and in the future operations of the analyses there is no embarrassment from a deposit of alum. The bisulphate of soda was prepared by adding an excess of pure sulphuric acid to the pure carbonate or neutral sulphate of soda, and heating it in a capsule until all the water had been expelled and sufficient of the acid to allow of the mass becoming solid on cooling. That obtained in commerce is not sufficiently pure. for the operation. The mass is allowed to cool, and water with a few drops of sulphuric acid are added to it, and the whole heated, when it soon dissolves with the exception of a little silica, that renders the solution milky, and a small quantity of undecomposed mineral, that is readily detected by rubbing a glass rod against the bottom of the capsule. The liquid is now filtered, and the filter is washed once with a little water; then with its contents it is placed in a platinum crucible, burnt completely, and the residue is heated with a little bisulphate of soda, which completes the decomposition; and when treated with water and a drop or two of sulphuric acid, all except the silica is dissolved. The liquid which passes the filter in this case is added to the first, and the analysis continued. The silica obtained is diminished by the quantity taken up from the mortar in order to arrive at what is actually contained in the mineral. The filtered solution is heated with a little nitric acid to convert all the protoxide of iron into peroxide, then treated with an excess of caustic soda, and a little carbonate of the same alkali; this redissolves the alumina first precipitated, and thus separates it from the oxide of iron and a trace of lime. The iron and lime are separated in the ordinary The pulverised emery is placed in a large platinum crucible with 6 or 8 times its weight of bisulphate of soda, and the mix-way: the alkaline solution of alumina was ture is heated over a lamp in the same manner and with the same precautions as are employed when using the hisulphate of potassa. From 15 to thirty minutes suffice acidulated, and the alumina precipitated with carbonate of ammonia. Thus analysed, the emery from different places gave the following results :-- Chemical composition. Water. 100. only using a little more of the bisulphate in the second decomposition; and, somewhat to my surprise, the decomposition was quite as perfect as in the other cases. I had nearly completed all my analyses in the manner detailed when this fact became known, so that I have but these two cases to report. The water which was found in the emery comes from the corundum. A very minute quantity of what has been estimated as water might be a little oxygen lost by the oligiste which is sometimes found in emery. Those emeries which contain the least water, everything else alike, are the hardest, as instanced by that from Kulah, notwithstanding the quantity of iron which it contains. The silica existing in emery is most often in combination with the alumina or oxide of iron, or with both; for this reason we must not always regard the quantity of alumina as an indication of the quantity of corundum in the emery. COMPOSITION OF MINIUM.* BY PROF. MULDER. THE Composition of minium may be represented by two different formula: according to M. Duinas, this oxide contains Pb3O', and should be regarded as a combination of 2PbO with Pb02: Pb304 2Pb0+PbO2. M. Winkelblech thinks, on the contrary, that minium contains sesquioxide of lead combined with protoxide: Pb304 PbO+Pb2O3. This sesquioxide, Pb2O3, exists and has been prepared by M. Winkelblech by adding hypochlorite of soda to a solution of oxide of lead in potassa. M. Houton-Labillardière examined a red and crystallised combination prepared in a minium furnace, the composition of which was expressed by the formula:— Pb'0' 2PbO+Pb2O3, or 3Pb0+Pb02. Finally, M. Longchamps examined a species of minium, which contained :Pb607 4 PbO+Pb203, or 5PbO+Pb02. From the foregoing it is evident that the composition of minium is variable. M. Mulder has analysed seven different kinds of minium, either by calcining that oxide and determining the loss of weight, or by treating it with nitric acid and weighing the peroxide left as a residue. The first process of analysis did not give accurate results, for minium always contains * Journal für praktische Chemie. small quantities of carbonic acid, which is disengaged with the oxygen. From M. Mulder's experiments, it results that most miniums have the composition Pb10=2PbO+Pb3Ó3, or 3PbO+Pb02, assigned to them by Houton-Labillardière. CONTRIBUTIONS TO THE HISTORY OF THE PANCREATIC JUICE.* BY M. J. L. LASSAIGNE. IT is known, from the interesting researches of MM. Bernard and Barreswil, that the pancreatic juice possesses the remarkable property of forming into emulsion fatty bodies of vegetable and animal origin, and of converting them into fatty acids and glycerine, at the temperature of 100° F. M. Bernard, in repeating lately, at the School of Alfort, in concert with M. Colin, principal anatomist of that establishment, the process by means of which he obtained it from animals, was kind enough to send me a small quantity of that juice, which he had himself extracted from an ordinary sized dog. The experiments to which we submitted it have enabled us to add some facts to those already known to physiologists, the principal of which may be summed up in the following propositions : 1. The action of the pancreatic juice on the oils is exerted even at the temperature of 53 to 59° F. in a few hours. Indeed, by moistening at several points a piece of blue litmus paper, with emulsion produced with olive oil and pancreatic juice, the moistened parts of the blue paper turned red by degrees from the circumference to the centre in presence of the air, and it is not necessary to maintain the mixture of oil and pancreatic juice for 12 or 14 hours, at the temperature of 100° F., as stated by the above-mentioned authors. 2. At the temperature of 59° F., the mixture of pancreatic juice and olive oil acidifies, after an equal time, in the vessels which contain it. 3. This acidification is produced in various gases, such as oxygen, hydrogen, nitrogen and oxide of carbon; the air does not seem, therefore, to participate in this singular reaction, which is perhaps due to a force of the same nature as that designated by Berzelius, under the name of catalytic force, and of which inorganic and organic chemistry present examples. 4. The pancreatic juice may retain its feeble alkalinity and its property of acting on the oil for several days. Comptes Rendus. 5. When the oil is modified by the contact of the pancreatic juice, sugar and gum, dissolved in that fluid, retain their neutrality, which denotes the entirely special action which it exerts on fatty bodies. ANALYSIS OF SUGAR FECULENCIES. into a point of view leading to new essays to prove or to disprove them, then I hope by my efforts to have made an advance, though but small, in that branch which you, the discoverer of diamagnetism have opened. I could not be entirely satisfied by that theoretical contemplation of the nature of diamagnetism which you, and after you Messrs. Reich, Poggendorff, Weber, and 48.940 Plücker have entertained.* This theory 37.486 requires the hypothesis, that in every mole0.146 cule of a magnetic substance subject to 0.155 external induction the magnetism is so distributed, that to the inducing south pole is 0-237 directed an induced north pole, and to the inducing north pole an induced south pole; 3.964 but that in diamagnetic substances the dis1-231 tribution takes place in such a manner, that in every molecule, to the inducing south 2-679 pole an induced south pole, and to the 1.320 inducing north pole an induced north pole is directed; or what is the same thing, that 3 842 the currents of the theory of Ampèere in magnetic substances are in the contrary direction to those in diamagnetic substances. I tried rather to explain to myself the phenomena by an hypothesis which M. van Recs+ had advanced; consequently I suppose that in magnetic, as in diamagnetic substances, the polarity of the molecules have the same direction; so that all the north poles are turned to the south pole, and all the south poles to the north pole of the inducing magnet; only with this difference, that in a bar of magnetic substance the intensity of the distribution upon the molecules increases from the ends to the middle, while in a bar of diamagnetic substance it decreases from the ends to the 100.000 100 grains of the dried matters were found to contain 5.42 grs. of nitrogen; consequently, the feculencics in their normal state contain 2.805 per cent. The exhausted animal charcoal, from the same refinery, was found when dried, to contain 2.82 per cent. of nitrogen. ON THE PHYSICAL DISTINCTION OF BY DR. VON FEILITZSCH. DR. FARADAY, to whom the following communication was addressed, transmitted it to the Editors of the Philosophical Magazine for publication in that excellent periodical, stating that he refrains from making any comment on the views of the author, his sole desire being to establish the date of a new theory, and that he has "left it almost in the author's language, that he might not misstate his views;" and we give insertion to it with the same view. Greifswald in Prussia, Dec. 3, 1850. SIR-If the statement of a new theory constitutes progress in science, when the phenomena already known are brought by it middle. The currents of Ampère in magnetic substances would be consequently more feebly directed in a given particle than in those nearer the centre of the excitation, but stronger than in those more distant; but in diamagnetic substances the reverse would be the case. These suppositions are permitted, if we attribute to the two groups of substances a diverse resistance to the magnetic excitation (a different coercive power). The particles of a magnetic body have a very feeble coercive power: then the distribution of magnetism must take place in such a manner, that the magnetism evolved in every particle by the primitive excitation acts on its part on the others, and particularly on * I have not adopted the view referred to. See Phil. Trans. 1850, p. 171.-M. F. Memoirs of the Netherlands Institution, vol. xii. P the neighboring particles. Because the molecules are situated very near one to the other, it may be supposed that this part of magnetism is stronger than that of the primitive excitation. But in diamagnetic bodies the coercive power is so considerable, that this portion of magnetism which appears by the excitation of the molecules one on the other is more feeble than that which is produced by the primitive excitation. A bar of magnetic or diamagnetic substance may be excited in two manners; either from the ends to the centre, or from the centre to the ends. A. The excitation from the ends to the centre is done when a bar is suspended between two magnet poles. 1. When the coercive power is such that the effect of the molecules on each other may be neglected, then every particle that is nearer to the magnet pole will be more strongly excited than the neighboring and more distant particle. If we observe two such neighboring particles near the external south pole, then will the more near repel a south pole with the intensity; the more distant will turn to a north pole with the intensity n', but in such a manner that n'<s. But outwardly these two excited magnetisms act with the difference of their power s-n'; but this in our case south polar, consequently of the same kind as the exciting south pole. The contrary will take place near the north pole, so that the disengaged magnetism, distributed over the bar, becomes south polar on that half which is turned to the south pole, but north polar on the other half that is turned to the north pole. A substance, where this takes place, is diamagnetic, it places itself equatorial. 2. When the bar of a magnetic substance is so qualified that the separating action of the molecules on each other must be taken into consideration, then it can become so strong that the molecules in the middle of the substance are more strongly magnetic than at the ends. If we observe, once more, two such particles near the external south pole, the south pole of the nearest will tend to recede by an intensity 8, from this external south pole, but the more distant will turn towards it a north pole of the intensity n', but in such a manner that n,' <s,. Outwardly the two will act with the intensity n-8, but this is north polar, therefore of a contrary nature to the exciting south pole. The contrary will take place near the north pole, so that the disengaged magnetism distributed over the bar becomes north polar on the half that is turned towards the south pole, but south polar on that half that is turned towards the north pole. A substance where this takes place is magnetic, it places itself axial. 3. Besides, of this observed disengaged magnetism, we must further consider that portion which becomes disengaged on the final surface of the bar, and which cannot be compensated by the neighbouring particles. This is always of a contrary nature to the neighbouring exciting pole. In magnetic bodies it supports the effect of the disengaged magnetism developed in the bar; in diamagnetic bodies it acts in the contrary direction, and it is to be thought that sometimes it even is preponderating. Perhaps this might be the cause of the feeble magnetism that you observed in platinum,palladium and osmium. B. An excitation from the middle to the ends occurs if we place a bar in an electrical spiral; but in this case all the substances must gain the same polarity as the iron. To prove that, I placed a thick bar of bismuth in a very strongly acting spiral, which was excited by four cells of Mr. Grove, every one of 12 square inch of platinum plate. I set this spiral on one side, and near to a little declination-needle suspended by a silk thread, and I compensated its effect by a steel magnet which I adjusted on the other side of the needle till the latter was returned to its first place. When I withdrew the bismuth bar out of the spiral, then the needle declined in favor of the compensating magnet; but if I restored it again in the spiral, then the needle declined in favor of the spiral Unfortunately the poverty of the physical establishment of our university did not allow me to test other substances than the bismuth, but I shall supply this defect as soon as it is to be done. You will allow me the consequence that diamagnetism and magnetism are only modifications of the same power, which are produced partly by the coercive power of the substances, partly by the different manner of excitation. Applying the former to the theory of Ampère, I was startled, because it has hitherto taught only that currents which are parallel and directed in the same way attract, but if they are parallel, and not directed in the same manner, they are repulsive; therefore, that a current, moving in the direction of the hand of a watch, in a spiral produces a south pole on the entrance point in the spiral, but a north pole on the egression point. Hitherto, only such spirals have been constructed in which the current in every winding shows an equal intensity. But I tried to arrange spirals of the following kind :-One of them is in such a |
