reaction shows the unfitness of palladium chloride in quantitative analysis for the separation of iodine from bromine and chlorine, because, if potassium ferrocyanide is present in the solution, faulty results may be obtained, as in this case iodine is not precipitated in the form of palladium iodide. The resulting greenish solution, on being boiled, yielded a solution of a beautiful dark green colour, which is palladium ferrocyanide (PdFeCys). It was remarked during the experiments that iodine in lumps easily dissolves in a boiling solution of potassium ferrocyanide, the colour of which remains yellow. In the green solution of palladium ferrocyanide obtained as mentioned above, the iodine dissolved in potassium ferrocyanide was not detected by starch; thus iodine must be supposed to be chemically combined with potassium ferrocyanide, and is, as I suppose, a molecular combination. In the formation of palladium ferrocyanide iodine has no action, because the same green solution of this salt is obtained by adding palladium chloride to a solution of potassium ferrocyanide free from iodine. Potassium hydroxide in the form of an aqueous solution, without being heated, rapidly dissolves the palladium ferrocyanide, yielding a yellow solution, containing free KyFeCy6. It must be mentioned that bromine easily dissolves in a solution of potassium ferrocyanide, forming a molecular combination. many c.c. of standard ammonia solution are run as will be deemed requisite to give a colouration equal to that yielded by the distillate, pure distilled water is used to fill up to the 100 mark, and 2 c.c. of Nessler, thus making the level of the liquid also in this cylinder B to reach 102. The usual time is allowed to elapse before the tints are compared. Supposing the liquids to be of different depths of colour, the glass tap of the cylinder which contains the darker liquid is opened, and some of the liquid is allowed to run out quite slowly, while the observer looks down the tubes in the direction of the axis, towards a sheet of white paper. The colours will get more and more of the same shade and tint, till at last no more difference can be observed. The glass tap is now closed, and the division is read off. It is easy to calculate now the quantity of ammonia actually present in the distillate. Supposing cylinder A, containing the distillate, appear the darker, and into B 5 c.c. of standard ammonia have been run, the liquid in both having been made to reach 102 as described, and, after equalisation of colours, the height of liquid in A was 76. We have then 76:5 = 102: x; x = 6.71 c.c. of standard solution has been put into B, and the level Supposing, on the other hand, that too great a quantity of the liquid in that cylinder, after equalisation, be 76: then we have1025 = 76 x ; x = 3'72 c.c. If the distillate amount altogether to 163 c.c., then the whole of it contains as much ammonia as corresponds to3'72 X 163 c.c. = 606 с.с. In a solution of potassium ferricyanide (K3FeCy6) iodine also dissolves, yielding a reddish yellow liquor: in this solution palladium chloride does not give the palladium iodide, and does not yield the green palladium ferrocyanide; the liquor remains reddish yellow; potas-tity of ammonia. There is no difficulty whatever in sium hydroxide colours this solution red. These experiments prove that palladium salts must be very carefully used in analyses for the detection of iodine, because in presence of potassium ferrocyanide or potassium ferricyanide the iodine is not detected, and cannot be separated from bromine or chlorine by palladium chloride. So as gold salts give, with ferrocyanide of potassium, also a green colouration, the K,FeCy6 as a reagent may give faulty results, as it was remarked that palladium salts give the same colouration. I conclude my paper by observing that if palladium salts are used as a reagent for iodine, the preliminary analysis must be very carefully executed, in order to be quite convinced of the absence of double ferrocyanates of potassium and other cyanides. As I showed in my paper in the CHEMICAL NEWS (vol. xxxii., page 242) that in presence of alkaline sulpho-cyanides (KCNS, NH,CNS, &c.) iodine is not precipitated by palladium nitrate or chloride. One single experiment thus gives accurately the quan noticing the right point, and, since the observer looks straight down the tube (not, as Frankland recommends, obliquely), the sinking of the level, whilst the tap is open, cannot be noticed at all, and no inconvenience can arise from the different height of the columns of liquid in the two cylinders. Of course, after the right number has thus been found, correct volume of standard ammonia to the pure distilled a supplementary experiment may be made, adding the water in B; but in all cases the figures will agree within I-10th c.c. These graduated cylinders with glass taps may be procured, I believe, from Messrs. Townson and Mercer, Bishopsgate Street, London. Care should be taken to have them perfectly cylindrical, in order to ensure equal value of the different divisions. The same method as described may be used in all other chlorimetric estimations, as of lead and iron in water, of copper, &c. 186 Estimation of Free and Albuminoid. Ammonia in Waters. in Dublin, taking as the standard of comparison the water of the Liffey, near where the sewage is discharged into the river. The results of my examination, conducted during November and December last, in the College of Science Laboratory, are now laid before the Royal Irish Academy. Altogether twenty-nine of these street-waters were examined; the samples dealt with were collected in my presence at the times and places stated in the Table appended to this paper; the mud, also, left from some of these pools was examined for ammonia, which reached two parts in the hundred, calculated after allowing for moisture expelled at 212° F. The river water was collected at intervals during the two months from four different places, namely at Eden Quay, Aston's Quay, Burgh Quay, and Sir John Rogerson's Quay, four hours after high water at Dublin bar. The method employed for determining the quantity of ammonia yielded by these waters and muds is that devised by Messrs. Wanklyn and Chapman. This process is almost universally allowed to be the best yet made known for ascertaining the character of the nitrogenous matter in CHEMICAL NEWS, waters; its quantitative results are accurate, and they The average of free ammonia from the four samples of the river is o‘0982, or under of a grain in the gallon; the average of albuminoid ammonia from the same is o'0779, or under of a grain in the gallon. 29 Aston's Quay December 15 Sir J. Rogerson's Quay It may be interesting to note that the examination ofĮ the river water referred to as having been made by other workers in the College of Science Laboratory, in 1874, gave a result equal to my average in 1875; thus showing a remarkable constancy in the state of the Liffey. It may also be remarked in passing that my average for free ammonia is less, but for albuminoid ammonia is greater, than the average Messrs. Wanklyn and Chapman reported as that of the Thames at London Bridge, in June, 1867 that river, the tide being at two hours flood, yielding free ammonia =0'1232 of a grain per gallon; and albuminoid ammonia =0'0245 of a grain per gallon. The average of free ammonia obtained from the 29 street-waters is 17 grains to the gallon, that is, over 170 times the like average from the river. The average of albuminoid ammonia from the street-water is 3 grains to the gallon, or 38 times the Liffey average. It will be seen by the Table, that from three out of the four river samples, the quantity of free ammonia was under that yielded by any of the street-waters, except at Stephen's Green, East and South. The maximum of free ammonia from the river was at Burgh Quay, and only reached o∙175, or less than of a grain to the gallon; whilst the maximum of free ammonia from the street-waters, namely, at Moss Street and Poolbeg Street, was 105 grains to the gallon, that is, exactly 600 times greater than the river maximum. The least impure of the 29 street-waters yielded nearly three times more albuminoid ammonia than the most impure sample of the river water; for instance, the surface-water at Merrion Square South being the best of the street-waters, yielded o 280 of a grain against that obtained from the river at its worst, namely, o 098 of a grain, or nearly 3 to 1. But the bad pre-eminence of the water in Moss Street and at Peter Place (corner in Adelaide Road), and in Lee's Lane, off Aston's Quay, namely, 10 and 1015 and 112 grains of albuminoid ammonia from one gallon of each water, respectively, is more than 100 times greater than the Liffey maximum. Messrs. Wanklyn and Chapman conclude from a wide induction of experiments that "the disintegrating animal refuse in the river [Thames] would be pretty fairly measured by ten times the albuminoid ammonia which it yields." In this way, the average of such refuse in the Liffey is 0.779, or just of a grain in the gallon; whilst the average of such refuse in the street-waters is 29 grains to the gallon. That much of this enormous amount of animal matter thus in our midst must, if not rapidly removed, take forms that will vapourise, seems all but certain, since the conditions for spontaneous decomposition may be said to be always present; there are the moisture and heat required for this chemical change, and then there occurs at intervals the drying up of these stagnant pools. My examination of these street-waters found, as might be expected, sulphuretted hydrogen, with other sulphides and very offensive volatile substances. What the effect must be on the people's health who dwell in an atmosphere contaminated by exhalations such as these, it is not for me to determine; this paper simply records the facts of the case, leaving conclusions to those physicians who make such researches their peculiar study. But without knowing the least of the little that is known, even to the medical faculty, about either the chemical or the germ-theory as to the propagation of disease, yet one of the unlearned, like myself, having but ordinary sagacity, might correctly conclude that the continued presence of so much dirt in the streets would go far to account for the high death-rate (33 to the 1000 yearly) lately recorded for Dublin, a city whose situation, other things being equal, might mark it out as one of the healthiest in the Empire. The London Times, reviewing "Ireland at the close of 1875," laid this to our chargethat "dirt reigns, and slays its thousands in Dublin and elsewhere." Whatever is to be done with our street sewage, whether it is still to defile the natural purity of the river, or to be applied to improve the land, or only to be thrown away, with great cost, into the sea; whatever be the destination of this noxious mass, whether it is to be good, bad, or indifferent, it certainly appears, from the results now laid before the Academy, that better scavenging and a level surface for the streets is at once required. The Professor of Hygiene and Public Health in University College, London (Dr. Corfield), in reference to this subject, in the "Manual of Public Health," edited by Hart, states that:-"If the streets, roads, and ways of a town or district are allowed to become or to remain so out of repair as to become receptacles for filth, or to afford, by their inequalities, depressions in which foul water accumulates, it is in vain to look for beneficial results from other sanitary measures." Hence it passes into a second cylinder where expansion takes place; the processes taking place here in the reversed order from what ensues in the compression cylinder, and the effect agrees exactly with that of an expansion steam-engine. The air here becomes very cold and is forced by the return of the piston into the freezing chamber where the ice boxes stand. After passing through this apparatus it arrives anew in the compressioncylinder to repeat the same circuit. The expansioncylinder here corresponds to the evaporation-receiver in other machines. The distinction, however, must be noted that but a small quantity of air is kept in circulation, whilst in other systems a large stock of the matter inducing the cold is present in the state of a liquid. It will be seen that the course of the conversions is exactly the same as in a "caloric engine," but in a reversed direction, and the performance of the one and the other may be calculated by the aid of the same formula. The writer has carried out such a calculation,† from which, it appears, that when the air, at an initial temperature of 20° C., is compressed to 3 atmospheres and then cooled down to 30°; the theoretical yield is 5 kilos. of ice per I kilo. coal consumed, whilst at 2 atmospheres the yield is 6 kilos. The production is in general terms inversely as the condensation of the air or the difference of temperature thereby produced. But, on the other hand, the dimensions of the cylinders for a given yield must be so much the larger the smaller the condensation which is to be applied, as appears at once on a close examination of the procedure. The actual performance of the machine may perhaps be considered equal to one-half of the theoretical yield. Hence it appears that the air machine is far "Berichte über die Entwickelung der Chemischen Industrie Während des Letzten Jahrzenends." t Bad. Gewerbz., 1869, Appendix Number, 188 Certain Methods of Physico-Chemical Research. inferior in its performance to the ammonia machine.* The reasons are the same which have been already advanced in the comparison of the ammonia and the ether machine. The efficacy of the machine may, however, be considerably increased, if, as we shall further explain below, the air is at once cooled during compression, so that it cannot become heated, in which case the cost of compression is much reduced. An advantage of the air machine as compared with other systems is that no offensive or combustible substances are brought into play, and that there can occur no waste of a costly material. An air machine is mentioned for the first time in 1863.t It was patented in England in April, 1862, by A. C. Kirk, of Bathgate. It consists of upright cylinders, the lower part of each being connected with the upper part of the other by a channel, fitted with a valve opening upwards. The pistons have valves opening downwards. The lower covers of the cylinders are kept cold by a stream of water, whilst the upper give off cold to salt water. According to the somewhat obscure description the action is as follows:-The piston of the cylinder a on descending compresses the air below it, and expands that above it, the compressed air being forced into the upper part of the cylinder b. On the ascent of the piston a the expanded air passes through the valve of the piston from the upper into the lower part of the cylinder, whilst the piston receives above at first compressed air from the lower part of the cylinder b, which, when the latter is emptied, begins to expand and to be cooled. The same processes take place in the cylinder b. Consequently one and the same quantity of air is always employed, which circulates from one cylinder to the other. It is asserted that I horse-power yields, in twenty-four hours, 106 kilos. of ice, the yield of the ether machine being 1105 kilos., =2 kilos. ice per kilo. of coal. In Young's paraffin works at Bathgate there was at that time a machine which turned out in twenty-four hours 2 tons or 2032 kilos. of ice. The result is somewhat small; the cooling surfaces of the cylinders are certainly not large enough to take up heat and cold quickly and completely. Indeed a series of theoretical objections might be urged against the construction of the machine, which is very simple. In 1864 it was announced that this machine was still at work in Young's establishment, producing a ton of ice with the consumption of a ton of coal, worth (then) four shillings. It was also declared that its efficacy was equal to that of the ether machine. This would be a far smaller yield. (To be continued) PROCEEDINGS OF SOCIETIES. CHEMICAL SOCIETY. Professor ABEL, F.R.S., President, in the Chair. Ar this meeting (which was a special one) Professor of Physico-Chemical Research." After a few preliminary remarks, in which he observed that the address must necessarily be of a somewhat discursive nature, he exhibited and described the apparatus employed by him many years ago for determining the heat developed during the combination of gases. It consisted of a thin copper cylinder, into which the mixture of hydrogen with excess of oxygen was introduced, closed by a screw top, with an apparatus attached for igniting a fine platinum wire in the interior of the vessel by means of an electric current. This was placed in a calorimeter, and the whole in a copper box, where it could be rotated so as to equalise the temperature of the water. After the rotation the temperature of the calorimeter was taken, the explosion effected, the apparatus again rotated, and the temperature read a second time, giving, after the necessary corrections had been made, the heat developed by the union of the known quantity of hydrogen with water in the proportion to form water. For the combustion in oxygen of solids, such as sulphur or carbon, a somewhat similar but larger apparatus was employed. The only experiments yet made to ascertain the heat developed by the direct combination of chlorine, bromine, and iodine had been made by him. He had at first experienced some difficulty in the case of potassium, as no glass vessels would resist the heat developed by its union with chlorine. This difficulty had been overcome by using a brass vessel, for he had found that dry chlorine was without action on both copper and brass. He also stated that in determining the heat developed by the mixing of liquids the only method of obtaining accurate results was to float a thin glass or platinum capsule containing one of the liquids on the surface of the other, and then by means of a fine pair of forceps pour out the contents of the capsule. Thomsen's results, obtained by another method, although not absolutely correct, were more accurate than those of Favre and Silbermann. Although frictional electricity was competent to decompose potassium iodide, yet it had been found that on passing the current by means of platinum electrodes through acidulated water no trace of gas was evolved: the wires became polarised, however, from which it might be inferred that the water was actually decomposed. It had seemed to him that the non-appearance of gas at the poles was due to its being dissolved in the large bulk of the liquid used, and he had consequently devised a simple arrangement by which this inconvenience might be avoided. Long platinum wires to serve as electrodes are fused into the ends of a couple of thermometer tubes, which are then filled with acidulated water by the simple expedient of boiling them for some time in the liquid. They are then inverted in a vessel of the same acidulated water, and a current of electricity from an electrical kite passed through by means of the platinum wires. In this way it was found that the water was quickly decomposed, and owing to the great tension of the electricity fifty or sixty of these couples could be arranged in series without any sensible diminution in the rate of decomposition, whilst it was well known that two or three, when introduced into the circuit of an ordinary battery, greatly enfeebled if it did not entirely stop the current. If one of these tubes filled with oxygen were placed over a solution of potassium iodide, and the silent discharge passed, the whole of the gas would be absorbed in about a minute. He desired particularly to draw attention to these tubes as affording a facile mode of experimenting on the action of the electric current on gases and liquids. He also exhibited the tubes In consequence of the low specific heat of the air, relatively large quantities must be employed, whence the cylinders and the resistance of friction to be overcome are very large. Pract. Mech. Journ., 1863, 113, Dingl. Pol. Journ., clxx., 241.mployed by himself and Prof. Tait in their experiments to Wagner, Jahresbericht, 1863, 568. However, a patent for an air ice machine was granted in England to one Nesmond, of Bellac, in France, as early as 1852. It compressed air to 20 atmospheres by means of a hand air-pump in a vessel like a boiler placed in cold water. After cooling the air passed into a second vessel where were the substances to be cooled or the air to be frozen, and escaped thence into the open air. It was asserted that a man could force the air into the compression-vessel in eight minutes, and thus produce 8 to 10 lbs. ice per hour. The action of the apparatus was therefore intermittent and not economical, and indeed the whole arrangement left much to be desired in point of convenience. Mech. Mag., 1864, 245. Dingl. Pol. Journ., lxxiv. demonstrate the diminution in volume which oxygen undergoes when converted into ozone. They consist of a wide tube filled with oxygen, and furnished with platinum wires, which is connected with a small U-tube containing concentrated sulphuric acid to serve as a gauge. After the oxygen had been measured at a constant temperature the point of the gauge was sealed, the discharge passed, and the apparatus brought to the original temperature. On now breaking off the sealed point of the gauge the diminution of volume could readily be observed; and if, under the enormous pressures employed, sometimes again sealed and heated to 300° C., and the volume again reaching 500 atmospheres, they pass through washers observed with similar precautions, it was found to be consisting of a pile of discs of perforated leather, which what it was originally, the ozone having been reconverted have been saturated with grease by soaking them in vacuo into oxygen. An apparatus on the same principle, but on a in melted lard. In this manner the apparatus was still larger scale, adapted for class experiment, was shown in perfectly tight even after the lapse of two or three years. action. It consists merely of a Siemens's induction tube He might mention that he had an apparatus made of iron, filled with oxygen, and connected with a narrow tube, the in which the pressure was communicated to the gas end of which dips into concentrated sulphuric acid, so as entirely by means of mercury, but he never succeeded in to serve as a gauge to measure any alteration in volume. getting it to remain perfectly tight for any length of time. As soon as the temperature of the apparatus has become The graduated portions of the thermometer-tubes proconstant, and the column of sulphuric acid in the gauge-jecting from the apparatus were surrounded by a suitable tube is stationary, the silent discharge from an induction arrangement for keeping them at a constant temperature coil is passed. The first effect, from the elevation of tem- by means of a current of water, or steam, or the vapour perature, is to expand the gas and cause the column in of some other liquid. When employing steam he had at the gauge to sink. After a time, however, the column times encountered some difficulty from drops of water begins to rise, showing the contraction in volume of the condensing on the graduated tubes, and thus interfering oxygen produced by the conversion of a portion of it into with the readings; these, however, could readily be reozone. It seemed unlikely that this property of the silent moved by pouring in boiling water, which washed the discharge of altering the density of oxygen should be con- tubes thoroughly. He had found great difficulty in emfined to that element, and he had tried its effect on nitro- ploying the vapours of liquids other than water, owing to gen and chlorine, but with negative results. He had the impossibility of obtaining them in any quantity in a hoped for something different in the case of chlorine, for pure state so that they would boil at a constant temit was a curious fact that although platinum might be left perature. He also described the means by which he had for years in contact with chlorine without producing any ascertained that mercury did not absorb either air or careffect on the metal, yet it was immediately attacked when bonic anhydride in the slightest degree, and mentioned an electric current was passed. The Lecturer then passed that although under very high pressures the capacity of on to his apparatus for determining the latent heat of the tubes was slightly altered, such alteration was not vapours, pointing out the great advantage of having it of permanent, and then proceeded to give a brief abstract of small size, since the experimenter was thereby enabled to the results which he had just laid before the Royal Society work with small quantities of material, for they all knew at the Bakerian Lecture on the natural gaseous states of how extremely difficult it was to obtain liquids which matter, and the way in which they differ from a theoretiwere perfectly pure in quantity. He was in the habit of cally perfect gas: the product of the pressure into the passing the vapour of the substance directly from the volume being invariably less than unity, whilst with a vessel in which it was dried over calcium chloride, so as perfect gas it would be unity. It is thus shown that gases to avoid any chance introduction of a trace of water, a condense more than they would if Boyle's law were cormatter of the utmost importance when the high specific rect. After some remarks on the air manometer, which heat of water is considered: 1 per cent of water in a liquid he said was an almost perfect instrument up to 200 atmowould often cause an error of 10 per cent in the latent spheres, the Lecturer concluded amidst great applause. heat. The determination of the latent heat of vapour was a very large field for chemists to work in, as at present scarcely anything had been done in it. After some remarks on the construction of graduating engines, in which he recommended the use of a very short screw, it being impossible to obtain a long one which was perfect, he proceeded to describe the construction and methods of working with his apparatus for observations on the behaviour of gases under great pressures. The thermometer-tubes employed in these experiments are made of a special kind of glass, and joined at one extremity to a wider tube, which is cut off and ground at the end. A slight swelling is made in the thermometer-tube towards the lower end to serve as a shoulder, on to which and for some distance down the tube shoemaker's thread is wound and covered with cobbler's wax, so that when firmly pressed into the perforated gun-metal cover of the pressure apparatus it forms a perfectly tight joint. The lower end of the tube dips into a glass vessel containing mercury, and the upper one, after the gas has been introduced, is carefully sealed. The accurately graduated and calibrated tubes are filled by passing a current of the pure dry gas, carbonic anhydride for instance, through them for some hours. The end is then carefully sealed, so as to cause the bore to be as perfectly conical as possible. This is a matter of considerable difficulty, but may generally be effected by keeping the tube vertical, and rotating it slowly before the blowpipe flame. The glass tube containing the mercury, and into which the lower end of this pressure-tube is plunged, is introduced into the gun-metal apparatus for communicating the pressure, and which is filled with water, the whole being screwed up tightly. The desired pressure is obtained by means of screws at the bottom of the apparatus, which being screwed into the water diminish the capacity of the vessel, the pressure thus produced being transmitted to the gas in the pressure-tubes through the mercury. In order to make these screws quite tight | The PRESIDENT then in a short speech expressed the thanks which they owed to Prof. Andrews for his most interesting lecture. The Lecturer afterwards exhibited the striking experiment of the action of heat on liquid sulphurous anhydride in causing it to pass into that curious" intermediate state" in which it is neither liquid nor gaseous. PHYSICAL SOCIETY. Prof. GLADSTONE, F.R.S., Vice-President, in the Chair. THE following gentlemen were elected Members of the The SECRETARY read a communication from Sir John Conroy, Bart., "On a Simple Form of Heliostat." The defect of Fahrenheit's heliostat, in which the beam of sunlight is reflected by a mirror moved by clockwork in a direction parallel to the axis of the earth, and then in the required direction by a fixed mirror, consists in the great loss of light. The author substitutes two silvered mirrors for the looking-glasses usually employed, and he has shown that the loss of light with this arrangement is less than when the light is once reflected from a looking-glass. Mr. S. P. THOMPSON, B.A., B.Sc., then made a second communication "On the so-called Etheric Force,'" and described some experiments which he has recently made in the Physical Laboratory at South Kensington on the subject. The name was given by Mr. Edison-the inventor of the motograph-to the sparks obtained when a conductor is presented to the core of an electro-magnet, the coils of which are traversed by an intermittent current. The results of the experiments conducted as originally described not proving satisfactory, various other arrange |