Dec. 31, 1875. Nature and Laws of Chemical Action. quently the effect of mass; and the gaseous state, the resistance to condensation, decomposition, and fusion, are indications of great density. These being the characteristics of all elementary substances, some idea can be formed of their origin or the conditions of their formation. The density of their molecules resisting the action of all known terrestrial agents, the constituents must have existed far removed from the general effect of the gravitation of the planetary mass, either as gases in high altitudes of the atmosphere, or must have originated on other heavenly bodies of much smaller mass. The effect of the velocities of molecules represents the sum of the attractive forces contained in a given volume of gas, and is its expansive energy. Molecular density or elasticity is directly proportional to the gas volume, and so is density to the number of molecules; the relation between number of molecules and volume is, therefore, not a constant one, but changes as I m and the law of Avogadro-" equal volumes of gases contain equal numbers of molecules "—is incorrect. This law, although the corner-stone of modern chemistry, has never been firmly established, but found at variance with important physical and chemical facts. Its fallacy is proven by the relation which has been established, by the mechanical theory of gases, to exist between volume and specific gravity, to the effect that the velocities of gas molecules are inversely proportional to the square roots of the weights of volume, which is the same relation deduced by me from the general law of gravitation. As already shown, the value of the square roots increases with the decrease of volume; and it is evident that the velocity of gas molecules is equivalent to their elasticity, and this to the volume. = I The discrepancies of Avogadro's law are due to the same causes as those of Mariotte's-to condensation, dissociation, or decomposition. All these changes are the result of compression, for increase of temperature at constant volume is but another mode of compression, and the pressure of a surrounding colder medium produces in all cases of increase of temperature an effect more or less approaching to constancy of volume. The result of condensation or decomposition depends on the quantity of the individual molecular mass. The exceptional behaviour of H, increasing in volume under great pressure, while that of all other gases, under the same circumstances, decreases, can only be accounted for by disintegration or dissociation of the H molecules, all other gases undergoing partial condensation. The extent of the disintegration of gaseous aggregates is illustrated by the vapour of sulphur, I volume of which weighs At a temperature of 500° 95=3, density=0'58. 600° 72=21, 700° 40 = 1}, 860° 32=1, =0.67. 307 holds good for identical substances as long as there is no The co. molecules of C and Flare examples of identical these cases, the same effect as mechanical compression; masses chemically united. The attractive force has, in increase of 1 a reduction of volume amounting to one-half its amount being that of 1 molecule, and the effect at each of a molecular volume. The relations between increase of mass and volume are consequently 4H. To the number of molecules 2, 3, 4, 5 corresponds à dim- total reduction of volume is 3x4=12-8=4. and that the gaseous elements and Br and I, their com- density being the active chemical principle, multiple of densities are consequently 100 025=41. 3 =53; 1+1=1 is the increase of mass, 17=33. The sum of reduction and increase, 5 that is, IH, combining with 80, unites with F1 9:50, d=0'324 ; The density of the volume weighing 32, consequently the The densities of these masses are to the unit H as necessity, constantly reduce water vapour to a more The law of Avogadro, as also that of Boyle or Mariotte In natrium hydroxide, if the composition is- Densities-100, 0°30 1'00=3X0'35-5 0'350'30+5. 0'35 308 Colorimetric Method for Determining Copper. ON A COLORIMETRIC METHOD FOR DETER- By THOMAS CARNELLEY, B.Sc., F.C.S., LAST year I brought before this Society a paper (Proceed ings, vol. xiv., 2) on a colorimetric method for determining iron in waters, and as this method has been found convenient for estimating small quantities of iron in substances other than water, I thought it would likewise be useful to have a delicate and easy method of a similar kind for copper, and it is the description of such a method that forms the subject of the present paper. The reagent used is the same as in the case of iron, viz., potassium ferrocyanide, which gives a purple-brown colour with very dilute solutions of copper. This reaction, however, is not so delicate as it is with iron, for I part of the latter in 13,000,000 parts of water can be detected by means of potassium ferrocyanide, while I part of copper in a neutral solution, containing ammonium nitrate, can be easily detected in only 2,500,000 parts of water. Of the coloured reactions which copper gives with different reagents, those with sulphuretted hydrogen and potassium ferrocyanide are by far the most delicate, and as a preliminary, the comparative values of these two reagents were tested, with the following results, the determination being made in each case in 150 c.c. of water:- (1.) With H2S. I part of copper produces a colour in 2,500,000 parts of water. (2.) With K4FeCу6. (a.) In acid solutions, the colour produced being earthy brown, I part of copper produces a colour in 1,000,000 parts of water. (6.) In neutral solutions, the colour being purplebrown, I part of copper produces a colour in 1,500,000 parts of water. (c.) In neutral solutions containing ammonium nitrate, the colour being purple-brown, I part of copper produces a colour in 2,500,000 parts of water. From the above it will be seen that of the two reagents sulphuretted hydrogen is the more delicate, except in the latter case, when they are of equal value. But potassium ferrocyanide has a decided advantage over sulphuretted hydrogen in the fact that lead, when not present in too large quantity, does not interfere with the depth of colour obtained, whereas to sulphuretted hydrogen it is, as is well known, very sensitive. And though iron if present would, without special precaution being taken, prevent the determination of copper by means of potassium ferrocyanide, yet by the method as described below the amounts of these metals contained together in a solution can be estimated by this reagent. As the above results show, ammonium nitrate renders the reaction much more delicate; other salts, as ammonium chloride and potassium nitrate, have likewise the same effect. The method of analysis consists in the comparison of the purple-brown colours produced by adding to a solution of potassium ferrocyanide-first, a solution of copper of known strength, and secondly, the solution in which the copper is to be determined. The solutions and materials required are as follows:(1.) Standard copper solution.-Prepared by dissolving 0393 grm. of pure CuSO4.5H2O in one litre of water. I c.c. is then equivalent to o'1 m.grm. Cu. (2.) Solution of ammonium nitrate.-Made by dissolving 100 grms. of the salt in one litre of water. (3.) Potassium ferrocyanide solution.-Containing I part of the salt in 25 parts of water. A Paper read before the Manchester Literary and Philosophical Society. Among others I may mention that use has been made of this method by Wanklyn, in the indirect determination of alum in bread.-CHEMICAL NEWS, vol. xxxi., p. 67. (4) Two glass cylinders holding rather more than 150 c.c. each, the point equivalent to that volume being marked on the glass. They must, of course, both be of the same tint and as nearly colourless as possible. (5.) A burette, marked to c.c., for the copper solution: a 5 c.c. pipette for the ammonium nitrate, and a small tube to deliver the potassium ferrocyanide in drops. The following is the method of analysis:-Five drops of the potassium ferrocyanide are placed in each cylinder, and then a measured quantity of the neutral solution in which the copper is to be determined into one of them (A), and both filled up to the mark with distilled water, 5 c.c. of the ammonium nitrate solution added to each, and then the standard copper solution runs gradually into (B), till the colours in both cylinders are of the same depth, the liquid being well stirred after each addition. The number of cubic centimetres used are then read off. Each cubic centimetre corresponds to o'I m.grm. of copper, from which the amount of copper in the solution in question can be calculated. The solution in which the copper is to be estimated must be neutral, for if it contains free acid the latter lessens the depth of colour and changes it from a purple brown to an earthy brown. If it should be acid it is rendered slightly alkaline with ammonia, and the excess of the latter got rid of by boiling. The solution must not be alkaline, as the brown coloration is soluble in ammonia and decomposed by potash; if it is alkaline from ammonia this is remedied as before by boiling it off; while free potash, should it be present, is neutralised by an acid and the latter by ammonia. cyanide does not affect the accuracy of the method, as was proved by several experiments, for instance, when c.c. and 2 c.c. of the ferrocyanide were added to the two ammonium nitrate to each, then 7 c.c. of the standard cylinders respectively, water up to the mark, and 5 c.c. of copper solution produced in each an equal depth in Within moderate limits the amount of potassium ferro colour. In order to test the effect which the different salts might have on the accuracy of the method, 8.0 grms. of a mixture of the following salts, viz.:-Ammonium chloride, sodium chloride, potassium nitrate, calcium chloride, calcium sulphate, and magnesium sulphate, were dissolved with an amount of copper sulphate, containing o'101 grm. Cu. to 1 litre. Varying quantities of this solution following results, from which it is seen that these salts were taken, and the copper estimated therein with the have no detrimental effect: CHEMICAL NEWS, Copper found. 0'54 m.grm. 0'71 99 o'gi 39 Action of Metallic Magnesium on Certain Metallic Salts. From which it will be seen that lead when present in not too large quantity has little or no effect on the accuracy of the method. The precipitate obtained on adding potassium ferrocyanide to a lead salt is white, and this, except when present in comparatively large quantity with respect to the copper, does not interfere with the comparison of the colours. In the above experiments the proportion of lead to copper was as 5 to 1. 309 might colour the liquid, and dissolved in a little boiling water and a drop or two of nitric acid, if it is not all soluble it does not matter; ammonia is next added to precipitate the iron, the latter filtered off, washed, re-dissolved in nitric acid, and again precipitated by ammonia, filtered off, and washed. The filtrate is added to the one previously obtained, and the iron estimated in the precipitate and the copper in the united filtrate. The distilled water used in the Owens College Laboratory, and which is condensed by the apparatus made by Hirzel, of Leipzig, gave, on analysis by the above method, the following results, two litres of the water being use for the purpose : o'15 parts Culin 1,000,000 parts of water. The copper and iron in this case were evidently derived from the fittings of the condensing apparatus, which consisted in great part of these metals. WHEN I published my examination of the chalybeate spring at Sellafield, near Whitehaven (CHEM. NEWS, xxxi., 11), I was unable to offer any idea as to the origin of the water or from whence it obtained its solid constituents. Since then I have been able to trace it, and find that the spring is supplied chiefly by drainage from fields in its immediate vicinity and partly by a small drain from a pond about half a mile distant. The water has to percolate through several yards of earth, which at about 5 feet from the surface and extending to a considerable depth below consists of a clayey soil containing both ferrous and manganous oxide, thus clearly indicating the origin of the chalybeate nature of the water previously analysed. I append an analysis of a portion of the clayey earth dried at 212°. Silica Ferrous oxide When copper is to be estimated in a solution containing iron the following is the method of procedure to be adopted. To the solution a few drops of nitric acid are added in order to oxidise the iron, the liquid evaporated to a small bulk, and the iron precipitated by ammonia. Even when very small quantities of iron are present this can be done easily and completely if there is only a very small quantity of fluid. The precipitate of ferric oxide is then filtered off, washed once, dissolved in nitric acid and re-precipitated by ammonia, filtered, and washed. The iron precipitate is now free from copper, and in it the iron can be estimated by dissolving in nitric acid, making the solution nearly neutral with ammonia and determining the iron by the method given in the paper before referred to. The filtrate from the iron precipitate ON SOME is boiled till all the ammonia is completely driven off, and the copper estimated in the solution so obtained as already described. The following are the results obtained with solutions containing known quantities of iron and copper: Found. Copper. Calculated. об Iron. Found. Calculated. (1) 0'53 m.grm. 0'51 m'grm. (2) 0.69 (3) 0.79 (4) 0.66 When the solution containing copper is too dilute to give any colouration directly with potassium ferrocyanide, a measured quantity of it must be evaporated to a small bulk and filtered if necessary, and if it contains iron, also treated as already described. In the determination of copper and iron in water, for which the method is specially applicable, a measured quantity is evaporated with a few drops of nitric acid to dryness, ignited to get rid of any organic matter that PRELIMINARY RESEARCHES ON THE ACTION OF METALLIC MAGNESIUM By SERGIUS KERN, St. Petersburg. DR. J. H. GLADSTONE'S very interesting paper on the copper-zinc couple inserted in the CHEMICAL NEWS, vol. xxxii., p. 195, gave me an idea to try the action of metallic magnesium on the aqueous solutions of certain metallic Salts. The first salt which I took was cobalt chloride; the results of the experiments are as follows: A concentrated solution of cobalt chloride in water, with a piece of magnesium-ribbon, was placed into a tall glass. Evolution of hydrogen immediately commenced, and the solution was left to stand quietly in the laboratory for about a week; it was observed then that the evolution of hydrogen was nearly finished, and the solution was of a light rose colour. The magnesium ribbon during the experiments fell into pieces and was covered with a green mass. The solution was then stirred by means of a glass Simple Apparatus for the Estimation of Tannic Acid. (CHEMICAL NEWS, d, and all the green mass fell down in the form of a, precipitate, which was filtered from the liquor, washed, and dried over sulphuric acid. This peculiar precipitate was carefully examined as will be further explained. From the remaining solution the excess of cobalt chloride was precipitated by (NH4)2S in the form of cobalt sulphide. The CoS was filtered, and the clear solution obtained was tested for magnesium salts in case they were present; analysis showed the presence of this metal, so that a solution of sodium phosphate (HNa2PO4), with the addition of ammonia, gave in the analysed liquid a precipitate of (MgNH4PO4). The green mass examined under the microscope showed the presence of small pieces of undissolved magnesium, but most of the mass precipitated consisted of a green amorphous powder, which gives the following reactions: (1.) It is insoluble in water and alcohol. (2.) With nitric acid it gives cobalt nitrate (Co(NO3)2). The substance was heated in a test-tube with sulphuric acid in order to obtain free hydrochloric acid in case chlorine were present in the green mass. Reagents showed the absence of chlorine. This substance was found to contain a considerable amount of cobalt monoxide (CoO); it is formed during the experiments by the following reactions: : CoCl2+ Mg+H2O=CoO+MgCl2 + H2. This equation explains well, I suppose, the action of metallic magnesium on cobalt chloride. When magnesium is thrown into a solution of silver nitrate, this salt is very quickly decomposed, with the formation of silver oxide (Ag2O). I conclude this short notice by remarking that Dr. Gladstone's new work opens to the chemist a new and very valuable method for chemical investigations. ON A SIMPLE APPARATUS FOR THE ESTIMATION OF TANNIC ACID BY THE THE method devised by Müntz and Ramspacher* is based on the fact that when a solution containing tannic acid is forced through well washed untanned hide, that the hide fixes all the tannic acid and practically allows the other matters which may be in solution to pass without being absorbed. The difference, therefore, between the specific gravities of the solution before and after passing through the hide indicates, by reference to a table, the percentage of tannin originally contained in the solution. The apparatus described by Müntz and Ramspacher is expensive, and the time required to have one constructed would no doubt be considerable, so that it would not be worth while for chemists who have not a somewhat regular practice in the analysis of tannin materials to go to the trouble or expense of having such an apparatus made. The principle of their contrivance consists in enclosing the fluid to be tested in a short metallic cylinder open at both ends, the under end being covered by a piece of the untanned hide, the upper by a strong piece of vulcanised sheet caoutchouc. These are clamped firmly together by screws, and by means of a screw to which is attached a rounded metallic disc pressure is brought to bear on the caoutchouc, and the fluid thus forced through the hide. The contrivance which I have devised for this purpose, which answers perfectly, and may be made altogether in about an hour, is the following: Two strong ground-glass funnels with rather wide stems are taken, a circular piece of hard wood fitted on * Annales de Chimie et de Physique, September, 1875, p. 86. Dec. 1875. each (as shown in the drawing), the bottom part of which comes within the eighth of an inch from the top of the funnel; four holes are made through the wood, into which are inserted four ordinary long iron screws fitted with nuts; the hide is placed between the two funnels, the screws passed through the holes in the two pieces of wood, the nuts screwed on and tightened equally all round by a key; a funnel with a thin stem is then inserted into the larger stem of the top funnel and the liquor poured in; the stem of the under funnel is passed through an india-rubber cork fitted into a flask; the flask is Letts's Diaries.-According to their usual custom, Letts, Son, and Co. (Lim.) have issued a series of Diaries for the year 1876. To meet the requirements of all classes and professions, they seem each year to add to their already long list. The "Medical Diary," the Appointment Diary," and the Commercial "Tablet Diary" are especially useful. A new feature of the Office Editions of these Diaries is the Lists of Provincial and Colonial and Foreign Post Towns, their distance from London (or Dublin), Market Days, Names of Bankers, and their London Agents, Number of Postal Deliveries and Despatches, &c. ULTRAMARINE: ITS FORMATION DURING THE INCINERATION OF BREAD. By JAMES EDMUNDS, M.D., M.R.C.P., Medical Officer of Health, and Public Analyst for St. James's, Westminster. I Do not find any note of the fact that, at a certain stage in the incineration of bread, the beautiful ultramarine blue is formed. This occurs under circumstances which I have not yet sufficiently studied to enable me to reproduce it with certainty; but, if the heat be raised to very bright redness or be prolonged after complete incineration of the bread, the blue passes into a beautiful turquoise colour, then becomes green, then passes on into a rusty colour, and finally comes out as a pale fawncoloured lining to the botryoidal mass of ash. This is not further affected, even by a prolonged white heat. The tints are so suggestive of the presence of copper that only by very careful examination did I satisfy myself of the absence of that metal; and I find that the colours occur in the purest and finest bread, as well as in inferior samples. I should be grateful if other analysts would favour me with any observations which they may have made upon this point, and I hope soon to be in a position to submit for myself some further account. It is curious that copper should appear in all the textbooks as one of the agents ordinarily used for adulterating bread, and the question arises whether the supposed use of copper may not sometimes have been erroneously inferred from the occurrence in bread-ash of these beautiful colours. THE last of the acid nuisances to which I shall refer is that caused by the manufacture of superphosphate of lime. In the early days of this branch of industry, it was the practice to make superphosphate of lime by mixing chamber acid a little diluted with water, with ground coprolites, bones, and animal refuse of all kinds, by means of a shovel and an open trough. The fumes of acid gases and vapours which were thus freely evolved into the air were extremely offensive to the neighbourhood. At present the mixture is effected in a closed vessel in which a stirrer revolves horizontally. The best form of mixer is about 10 feet long and 4 feet in diameter. The materials which are used in the manufacture are ground coprolites, crushed bones, spent animal charcoal from sugar refineries, and animal refuse of all kinds. These are put into the mixer in proper proportions, and treated with water and sulphuric acid. The mixer has an upper opening for the admission of the materials, and a lower one for the exit of them. Both of these openings are secured with air-tight valves; and during the mixing, which lasts from five to ten minutes, the materials evolve vapours charged with organic fumes as well as the acid, and exceedingly irritating tetrafluoride of silicon, which is produced by the action of sulphuric acid upon the fluorides and silicates * A Paper read before the Society of Medical Officers of Health. Communicated by the Author, contained in the coprolites. These gases and vapours are conveyed from the mixer by a special shaft or flue which carries them first to a chamber, in which they meet a copious spray of water, and then through a coke scrubber or condenser supplied with a stream of water; and lastly, in some cases, through a lime purifier before they reach the furnace shaft. When the materials are thoroughly incorporated in the mixer, they are discharged through the lower opening into the chamber or den, in which, in the course of twenty-four hours, they consolidate. This chamber should also be air-tight, and ventilated into the same shaft or flue which carries the gases from the mixer to the condenser. If these operations are properly managed, they may be conducted without other offence to the neighbourhood than the faint acid smell which is inseparable from the exposure of the consolidated superphosphate; but if they are not well designed and managed, they are the cause of insufferable nuisance. The object of having a fine spray of water as the first absorbent of the acid gases is that the tetrafluoride of silicon is immediately decomposed when it comes into contact with water, forming hydrate of silica, which is deposited in a pulpy form, and an acid called hydro-fluosilicic acid, which the water dissolves. Now, if this were to take place in a scrubber packed with coke and supplied with downward flowing water, this hydrate of silica would soon clog the pores and apertures of the scrubber, and throw it out of action. Hence the necessity for decomposing the tetrafluoride of silicon in a chamber before it reaches the coke scrubber. And now, in concluding this brief outline of the processes which are most likely to receive attention from Medical Officers of Health, I may summarise the recommendations which I have ventured to submit as the best means of abating the nuisances referred to by saying: First, that all noxious and offensive operations should be carried on, as far as possible, in air-tight chambers, which can be ventilated by means of fans, or by the chimney draft. Second, that all condensible and absorbable gases and vapours should be passed through condensers and absorbents best suited for their absorption-as water in spray, and scrubbers charged with water, oil of vitriol, or alkaline solutions. Third, that, when necessary, these scrubbers should be supplemented with special purifiers, as hydrated oxide of iron, hydrate of lime, &c. Fourth, that organic vapours and sulphuretted hydrogen and empyreumatic matters should be conveyed to the furnace fire and destroyed. In carrying out this be condensed from the vapours by cooling them thopart of the process it is necessary that all steam should roughly before they reach the fire, as otherwise the fire is apt to be put out by them. The fire which is best suited for this purpose is that which is actually used in manufacturing operations, as special fires are very likely to be neglected; and the best place for the entrance of the noxious vapours is at the back of the ash-pit immediately under the fire bars, as by this means a draft is secured (by closing the ash-pit), and the vapours are made to pass through the glowing coals of the fire. Fifth, all offensive materials should be brought to the works, or carried away from them, in properly constructed carts or tanks, which can be closely covered; and all such material when stored at the works should be kept in close tanks or chambers, ventilated, when necessary, to the scrubbers or furnace fire. managed with care and attention to details-there being Lastly, the whole of the operations should always be no neglect of the sound condition of every part of the plant or working apparatus. With these precautions, which are by no means unreasonable or impracticable, the manufacturer of offen |