INORGANIC CHEMISTRY. Inorganic Chemistry. ii. 103 Composition of Chlorine Hydrate. A. BOUZAT and L. AZINI~ES (Compt. rend. l923,177,1444--1446).-Chlorine hydrate prepared in presence of liquid chlorine not water as the liquid phase has the formula C12,6H,0. A. L. MARSHALL and H. S. TAYLOR (Nature 1923,112,937-938).-In an attempt to test the validity of Nernst’s theory (A 1919 ii 208) of the wide deviation of the hydrogen-chlorine combination from Einstein’s photochemical equivalence law atomic hydrogen has been led into a mixture of hydrogen with chlorine and bromine respectively. The amount of hydrogen chloride formed appeared greatly to exceed that due to the atomic hydrogen present a result which would be anticipated from the theory. Electroisomerism The Constitutional Formula of Hypo- sulphurous ’’ [Thiosulphuric] Acid and the True Thiosul- phuric Acid.J. PICCARD and E. THOMAS (Helv. Chirn. Acta 1923 6,1032-1036) .-The conception of the acid H,S,O as thiosulphuric acid OH*SO,*SH implies that it is a mixed anhydride of sulphuric acid and hydrogen sulphide just as chlorosulphonic acid is a mixed anhydride of sulphuric and hydrochloric acids. Its properties do not agree with this conception for it decomposes not into sulphuric acid and hydrogen sulphide but into sulphurous acid and sulphur in aqueous solution. It is shown that a t the temperature of liquid air in carbon dioxide solution sulphur trioxide and hydrogen sulphide combine to give what is presumed to be the true thiosulphuric acid. In this compound the sulphur takes the place of negative bivalent oxygen in sulphuric acid.Ordinary ‘‘ hyposulphurous acid ” (thio- sulphuric acid) must be an electronic isomeride of the true thio- sulphuric acid the additional sulphur atom being neutral. In the true thiosulphuric acid the central sulphur atom is sexavalent ; in the isomeride it is quadrivalent. The difference can only be expressed by co-ordinative formulae thus E. E. T. Mechanism of the Hydrogen Chlorine Combination. . A. A. E. I i so+srr -011 - jH’ H’ [;zsv?ll 1; -orxJ L-On -o= ‘‘ Hyposulphurous acid.” Thiosulphuric acid. E. H. R.ii. 104 ABSTRACTS OF CHEIKICAL PAPERS. The Existence of Free Thiosulphrrm'c Acid in the Presence .of Fuming Hydrochloric Acid and the Preparation of Alcoholic Solutions of Thiosulphuric Acid.J. CASARES GIL and J. BEATO (Ber. 1923 56 [B] 2451-2453).-1f a concentrated solution of sodium thiosulphate ( 3 - 4 drops) is added to fuming hydrochloric acid ( 3 4 c.c.) sodium chloride is precipitated after which the clear solution can be preserved without change for about an hour a t 15" ; it gives the reactions typical of thiosulphuric acid. An alcoholic solution of thiosulphuric acid is obtained by the action of dry hydrogen sulphide on lead thiosulphate (dried at 105") suspended in alcohol. The precipitated lead sulphide is filtered and excess of hydrogen sulphide removed from the filtrate by a current of air. The acid decomposes in the course of a few days at about 28" into sulphur and apparently pentathionic acid. A. GUTBIER [with A. FIECHTL] (KoEloid. Z.1923 33 334-337).-Relatively stable sols of selenium may be prepared by evaporating on the water-bath to a syrupy consistency an aqueous solution containing equimolecular quantities of selenium dioxide and dextrose and then adding one drop at a time of con- centrated ammonia taking care that the solution remains syrupy. After cooling and mixing with water reddish-brown sols are obtained which after a short time are stable and contain about 0.016 g. of selenium per 100 C.C. The stability of the sol is increased by the presence of a slight excess of dextrose. The sols are stable on boiling but on freezing they are completely and irreversibly coagulated if there is no excess of dextrose. The sols are sensitive to electrolytes. Glycerol sols can be prepared in the same way as the hydrosol and have similar properties.Ammonia Equilibrium. A. T. LARSON and R. L. DODGE ( J . Amer. Chem. Xoc. 1923 45 2918-2930).-The equilibrium values for the reaction N2+3H 2NH have been determined at 10 30 50 and 100 atmospheres pressure for the temperature range 325" to 500". The following values observed for the percentage of ammonia at equilibrium are recorded a t 10 atms. pressure 360° 7-35; 400" 3.85; 450" 2.04; 500" 1.20; 30 atms. pressure 350" 17.80 ; 400" 10.09 ; 450" 5-80 ; 500" 3-48 ; 50 atms. pressure 3N" 25.11 ; 400" 15.11 ; 450" 9.17 ; 500" 5.58 ; 100 atms. pressure N O " 24.91 ; 450" 16.35 ; 500" 10-40. Equilibrium constants have been calculated for each of the pressure-temperature conditions inves- tigated. These constants are found to increase with increase of pressure.By means of empirical formulze the percentage of ammonia at equilibrium has been calculated for a temperature range 200-1,000" and a pressure range 10-100 atms. The Reduction of Azoimide. J. PICCARD and E. THOMAS (Helv. Chim. Actu l923,6,1039-1040).-The reduction of azoimide by chromous chloride in acid solution takes place according to the equation HN3+H,=NH,+N (cf. Briner and Winkler A. 1923 ii 485). E. H. R. H. W. Colloidal Selenium. J. F. S. J. F. S.INORGANIC CHEMISTRY. ii. 105 Vapoxlr Pressure of Nitric Oxide. H. GOLDSCHMIDT (2. Physik 1923 20 159-165).-Particulars are given of the deter- mination of the vapour pressure of nitric oxide at temperatures between -148" and -181". The results indicate that at To (Abs.) the vapour pressure of the liquid phase (measured in mm.of mercury) is given by the equation log p=6.92669-0~010801T+1*75 log T- '778*13/T'. The corresponding equation for the solid phase is log p = 6*m69-O-005895T+ 1-75 log T-837-42/T. The occurrence of considerable association amongst the molecules of liquid nitric oxide is established. From the results the following values of physical constants relating to nitric oxide are calculated b. p. -151-13" ; triple point -163.21" ; vapour pressure a t the triple point 170.2 mm. ; latent heat of evaporation a t respective temper- atures -151-13" 3199 cal.; -155" 3230; -160" 3289; -163.21' (liquid) 3324; -163-21" (solid) 3863; -165" 3872 ; -168" 3885; -173" 3902; -177" 3912; -183" 3923; latent heat of fusion a t the triple point 539 cals.& 1%. Hydrofluosilicic Acid. 11. .C. A. JACOBSON ( J . Physical Chem. 1923 27 761-770 ; cf. A. 1923 ii 561).-Experiments are described which show that silicon tetrafluoride and water vapour do not react at temperatures between 30" and 125". Four types of experiment have been carried out with the object of ascertaining the condition of hydrofluosilicic acid in the vapour phase. In the first case air was passed through dilute solutions of the acid a t various temperatures and the resulting products passed through water for absorption. In the second and third cases strong solu- tions of the acid were distilled fist a t the ordihary temperature and then by boiling with various desiccating agents introduced in the stream of vapour. In every ,experiment where the water was removed from the vapour mixture no trace of hydrofluosilicic acid was obtained in the receivers. In the fourth case an attempt was made to liberate the acid from its sodium salt by means of concen- trated sulphuric acid and to condense the acid in a receiver cooled by ice and salt.No liquid condensed because the sulphuric acid removed the water from the gas mixture leaving the apparatus filled with silicon tetrafluoride. The vapour density measurements made by Baur and Glaessner (A. 1904 ii 119) on the gas obtained by treating barium silicofluoride with sulphuric acid indicate the complete decomposition of hydrofluosilicic acid into hydrogen fluoride and silicon tetrafluoride. All the above results indicate that hydrofluosilicic acid is a non-volatile acid like carbonic acid and sulphurous acid and cannot exist under ordinary conditions in the vapour state.A. RUTTI and E. BOGGIO-LERA (Hem. A c d . Lincei 1923 [v] 14 1257132).-The explanation advanced by Lo Surdo (A. 1921 ii 331) of the divergence of the results of Ramsay Collie Patterson and Masson (A 1914 ii 727,847) from those uf Merton (A. 1914 ii 726) S t r u t t (A. 1914 ii 201) and Piutti and C a b s o (A 19-20 ii 311) is not valid (cf. Baly Ann. Reports 1913 37; 1914 411 J. S. G. T. J. F. S. Diffusibility of Helium through Thuringian Glass.ii. 106 ABSTRACTS OF CHEMICAL PAPERS. fiince the amount of helium able to penetrate from the air into a discharge tube even one of large surface kept for many hours at 260" is about 1% of the quantity recognisable spectroscopically by the methods used by the above investigators.The velocity of d8usion of helium through Thuringian glass is proportional to the pressure and increases very rapidly with rise of temperatiire being apparently an exponential function of the latter. The Free Electron Characteristics of Sodium-Potassium Alloys. C. V. KENT (Physical Rev. 1923 [ii] 22 479485).- The free electron parameters of the sodium-potassium alloys have been calculated from optical data obtained by Morgan (ibid. 1922 20 204). The number of free electrons per atom is about 1.5 for all the alloys but with an indication of a minimal value of 1.2 for the one-third sodium alloy. The frequency of impact of a free electron with molecules (1 to 3 x 1014) increases linearly with increa.se of either constituent to a maximum for the compound NaK sup- posed to exist in the liquid alloys.Calculated resistivities agree with those experimentally determined. Displacement of Metals from Solutions of their Salts by Less Electropositive Elements. I. Replacement of Sodium and Potassium by Magnesium and Aluminium. F. W. BERGSTROM ( J . Amer. Chem. Soc. 1923 45 2788-2794).-AmaI- gamated aluminium reacts with sodamide in liquid ammonia solu- tion to form a definite crystalline compound sodium ammono- aluminate to which any of the following formulae may be given A1(NH2),*NHNa,NH3 ; Al(NH,),,NaNH ; Na[AI(NH,),]. This compound loses one molecule of ammonia when heated in a vacuum above 90". The equations for the reaction are shown to be Al+3Na(NH2) Z A1(NH2)+3Na ; Al(NH,),+NaNH,= Al(NH,),*NHNa,NH ; 3Na+ 3NH3=3/2H2+3NaNH,. The actions of potassamide on amalgamated aluminium and on magnesium are analogous in character.An explanation is given which depends on the fact that dilute solutions of the alkali metals in ammonia are salt-like in character. The initial stages may be regarded as metatheses although actually involving equilibria which suffer continual displacement because of secondary reactions. A solution of sodium in liquid ammonia reacts with amalgamated aluminium to form the same sodium ammono-aluminate mentioned above. Sodamide is probably first formed and this then reacts in accord- ance with the equations above The mercury of the amalgam does not play an essential part in the reaction. 111.System Water and the Chlorides and Carbonates of Sodium and Potassium at 2 5 O . N. System Water and the Sulphates and Carbonates of Sodium and Potassium at 25". W. C. BLASDALE ( J . Amer. Chem. Suc. 1923,45,2935-2946; cf. A. 1918 ii 231 ; 1920 ii 237).-Certain optical and crystallographic proper- ties of the hydrates of sodium carbonate and of the hydrate of the double sodium potassium carbonate have been determined which T. H. P. A. A. E. J. P. S. Equilibria in Solutions containing Mixtures of Salts.INORGANIC CHEMISTRY. ii. 107 can be used in identifying these compounds by means of the micro- scope. The solubility data necessary for the preparation of com- plete phase rule diagrams for the systems H,O-Na,CO,-KCl and H20-Na&03-K,S04 a t 25" have been determined. Triple Salts.F. E P H R A ~ (Helv. Chim. Acta 1923 6 920- 930) .-The important part played by space considerations in deter- mining the possibility of formation of complex compounds is well illustrated by the series of triple nitrites of which the best known member is the salt K,P~[CU(NO,)~]. The extent to which each of the constituent metals can be replaced by related metals is deter- mined by the atomic volumes of the metals. The copper (at. volume 7.1) can be replaced by nickel (6.6) cobalt (6-Q and iron (7*1) but not by any metal with greater atomic volume such as manganese (7.4) or zinc (9.2). The potassium (45.3) can only be replaced by rubidium (56.2) caesium (70.4) and ammonium not by sodium (22.9) or thallium (17.2). The lead (18.2) can be replaced only by calcium (25.2) strontium (32-6) and barium (36-3) save under exceptional conditions.When nickel with the amdl atomic volume 6-6 replaces copper it is possible to introduce cadmium (13.0) and mercury (14-1) in place of the bigger lead atom. Most of the known triple salts are derived from weak acids but one triple chloride 6KCl,CuC1,,3HgC1,,2H20 has been described (von BonsdorfT Ann Phys. Chem. 1834 33 81). The existence of this salt could not be confirmed but a new triple potassium copper mercuric chlmide 8KC1,CuCl2,4HgC4 was dis- covered. It separates from a hot aqueous solution of its components in yellowish-brown needles. It is not stable in the cold in contact with the mother-liquor Attempts to prepare similar salts contain- ing nickel or magnesium instead of copper or bromine instead of chlorine were unsuccessful.A triple chloride of another type KCuCI,,2KPbC13 was discovered however. It can only be obtained from a solution of its constituents in concentrated hydrochloric acid and forms microscopic brownish-yellow prisms. Another type of salt which was prepared containing three merent metals has the composition K,[CU(NO,)~,H,O] + BK..JHgCI,,H,O]. It crystallises in thick black prisms and is probably to be regarded as a mixture of its constituents possibly as a solid solution. The known potassium copper nitrite is found to have the formula K,[Cu(NO,),,H,O] instead of K,[Cu(NO,),]. The following new triple nitrites are described cclesium barium nickel nitrite Cs,Ba[Ni(NO,),] forms an orange-brown powder very sparingly soluble in water ; cmium lead wpper nitrite Cs,Pb[Cu(NO,),] sparingly soluble black microscopic crystals.A new ammonzum rnanganwe carbonate (NH4)&03,MnC03,4H20 microscopic prisms was also obtained The Fusibility of the Ternary System Sodium Fluoride- Calcium Fluorid+Aluminium Fluoride. P. P. FEDOT~EEV and W. P. ILJINSKY (2. anorg. Chem. 1923,129,93-107).-The examin- ation of the system AlF,-NaF (A. 1913 ii 324) has been completed and the investigation extended to the ternary system with calcium J. F. S. E. H. R.ii. 108 ABSTRACTS OF CHEMICAL PAPERS. fluoride the concentration triangle being fully worked out. The system NaF-CaF shows st simple eutectic a t 810" 6'7.5 mol.O/b NaF. Fusions of calcium fluoride with aluminium fluoride are only realis- able between the. limits 30 mol.% and 60 mol.% AlF ; the eutectic is at 820" 37-5 mol.yo AlF and there is a marked tendency to supercooling with formation of solid solutions of the components. The system NaF-AlF has two maxima one corresponding with cryolite 25 mo1.X NaF m. p. 1,000" which melts without decom- position the other with a compound with 40 mol.yo NaF which melts with decomposition a t 725"; the minima are a t 885" 86 mol.% NaF and 685" 53.4 mol.% NaF. The temperatures of invariant equilibrium for the ternary system are 780" 705" and 675" the minimum point for the space pyramid lying between the compositions NaF CaF AlF = 58.7 5.9 354 and : 56.5 8-3 35.2 rnol.% respectively; the diagram shows Crystal Structure of Sodium Chlorate.N. H. KOLEMEIJER J. M. BIJVOET and A. KARSSEN (2. PhysiE 1923,20,82).-Referring to the work of Kiby on the crystal structure of sodium chlorate (Ae 1923 ii 687) the authors point out that the calculation of the parameters relating to light atoms from the observed intensities of the higher orders of X-ray reflections making the approximate assumption that the reflecting power is proportional to the elec- tronic number and independent of the angle of deviation of the rays is unjustifiable. Vappur Pressures of Lithium Chloride Solutions at 20". B. F. LOVELACE W. H. BAHLKE and J. C. W. FRAZER ( J . Amer. Chem. Soc. 1923 45 2930-2934).-The lowering of the vapour pressure of water due to dissolved lithium chloride has been measured at 20" and in the concentration range of 0.1N to 1.ON.An improved method for removing air from the solutions before measuring is described. This consists in introducing the solution as nearly air-free as possible into the bulb which had previously been pumped air-free and rapidly distilling a small portion of the solvent a t the pressure of its vapour into a bulb containing phosphoric oxide. The observed lowering of the vapour pressure has been compared with the values calculated from freezing-point measurements and a difference of -0.015 to +0.014 mm. between the two sets of values found J. F. S. An Explanation of the Explosive Decomposition of Bleaching Powder and the Mode of its Decomposition at Higher Tern- peratures. s. OCHI ( J . Chern. Ind. Japan 1923 26 978-983).- When bleaching powder is heated above loo" the chlorine-forming oxygen-forming and chlorate-forming decompositions occur together.If it contains a comparatively large amount (e.g. 18-01 %) of water it is very rapidly decomposed a t temperatures above 100" and the chlorine-forming and the chlorate-forming decompositions predominate. In this case explosive decomposition may not occur but suoh a powder is unsuitable for storage. By decreasing the thirteen regions. s. I. L. J. S. G. T.INORGANIC CHEMISTRY. ii. 109 water content of the powder the mode of decomposition is changed to the oxygen-forming one which proceeds mildly a t first but advances suddenly when the temperature is raised a little higher than 150"; explosion then occurs. The decomposition may be expressed as follows OC1*CaCl,H,0=CaC12,H20+ 0+14,440 cal.The explosive decomposition may be brought about by external heating or by the accumulatioii of heat produced by auto-decom- position. K. K. The Reaction of Carbon Dioxide with Bleaching Powder. 8. OCHI (J. Chem. I n d . Japan 1923 26 1154-1161).-The action of carbon dioxide on bleaching powder is accelerated not only by the rise of the reacting temperature and the increase of the water content of the powder but also by the imperfection of crystallisatioii of the powder. The gas produced by the decomposition of bleaching powder is composed of chlorine only. On passing moist carbon dioxide or air containing carbon dioxide into bleaching powder at about 60" chlorine is produced; it is free from carbon dioxide when the velocity of the gas is well regulated.Chlorine containing a certain amount of carbon dioxide is purified in the same way. In making the powder with chlorine containing carbon dioxide it is concluded that the water content of the raw materials must be increased and the temperature of the bleaching chamber must be raised. K. K. W. L. BRAGG (Proc. Roy. SOC. 1924 [ A ] 105 16-39).-By X-ray analysis it is shown that the crystal structure of aragonite is based on the simple orthorhombic lattice. The cell the sides of which are of lengths 4.94 A. 7.94 d. and 5-72 8. contains four molecules of CaC03 and the symmetry is that characterising the space group &l6tL. The structure is built of calcium atoms and CO groups having a form almost identical with the CO groups in calcite. Calcium atoms are arranged on a distorted hexagonal close-packed point system intimately related in its dimensions to the distorted cubic close-packed point system associated with the calcium atoms in calcite.In aragonite the CO groups are arranged differently from the corresponding groups in calcite each oxygen atom being surrounded by three calcium atoms in the former crystal and by two only in the latter. Con- sidered as a whole the CO group lies between two groups of three calcium atoins in both crystals. A comparison of t'he observed int'ensities of reflection of the rays and calculated amplitude factors for aragonite shows that in accordance with the empirical law discovered by Sir W. H. Bragg in the case of calcite the intensity is proportional to the amplitude-factor and not to the square of the latter as suggested by theory.Twinning of aragonite crystals about the plane (1 10) is simply explained by the suggested structure. Hydration of Anhydrite. 11. G. WEISSENBERGER and B. SOINI (KoEZoid Z. 1923 33 290-296; cf. A 1923 ii 241).-The hydration of anhydrite has been investigated by measuring the VOL. CXXVT. ii. 5 The Structure of Aragonite. J. S. G . T.ii. 110 ABSTRACTS OF CHEMICAL PAPERS viscosity of suspensions of anhydrite in water a t 18" 30" 40" 50" and 62". It is shown that the addition of water to anhydrite proceed9 to a definite c!id value. The quantity of added water is dependent on the concentration and on the temperature but is independent of the size of the particles. The greater the concentra- tion and the lower the temperature the smaller is the amount of water added.The intensity of the combination with water achieved technically is approximately parallel with the internal friction of dilute suspensions measured viscosimetrically but not with the amount of water taken up. J. F. S. The Constitutional Formula of Barium Peroxide. J. PICCARD (Helv. Chim. d c t a 1923 6 1036-1038).-The strain t'heory renders it improbable that barium peroxide has the formula Ba<? whereas the double formula containing a six-membered ring Ba<Exg>Ba shoulcl represent a stable system. The ready formation of hariuin peroxide from barium oxide and mole- cular oxygen can be simply represcntecl without rupture of the oxygen molecule if the double formula be assumed thus Ba/'o--oNBa + Ba< O-O>Ba.The fact that sodiuiii per- oxide cannot be formed from sodium oxide and oxygen but only from sodium and osygen points t!o a similar oxidation mechanisin in this case Na+O~O+Na-+Na-O-O--Na. The mode of formation of many organic peroxides gives additional support to the theory. Crystal Structure of Magnesium Stannide. L. PAULING ( J . Amer. Chem. SOC. 1923,45 2777-2780).-Crystals of the inter- metallic compound magnesium stannide Rlg,Sn have been prepared and investigated by means of Laue and X-ray spectrum phot,o- graphs with the aid of the theory of space groups. This compound is found to have the calcium fluoride structure with d1,,=6-78&0.02~. The structure places eight magnesium atoms round each tin atom a t the corners of a cube and four tin atoms round each magnesium atom a t the corners of a tetrahedron.The closest approach of tin and magnesium atoms is 2.94*0-01 A. E. A. OWEN and G. D. PRESTON (Proc. Phpical SOC. 1923,36,49-65).-Particulars are given of an investigation by means of X-ray analysis of the respective structures of alloys constituting the a p p' 7 and E phases of the zinc-copper alloys. J. PICCARD and E. THOMAS (HeEv. Chim. Acta 1923 6 1046).-The solubility of cad- mium sulphide in dilute sulphurie acid is apparently greatly increased a t the boiling point that is the equilibrium in the equation CdSO4+H,S~CdS+H,SO4 moves to the left. It is now shown however that complete solution of the sulphide can be accomplished 0 7 0-0 0=0 E. H. R. J. F. S. X-Ray Analysis of Zinc-Copper Alloys.J. S. G. T. The Solubility of Cadmium Sulphide.INORGANIC CHEMISTRY. ii. 111 by passing a current of carbon dioxide through a suspension of the sulphide in cold dilute acid. The reaction is therefore subject to the usual mass-action laws. E. H. R. T. .W. RICHARDS and P. PUTZEYS ( J . Amer. Chem. Soc. 1923 45 2954- 2958).-The atomic weight of a sample of radioactive lead obtained from a mixture of minerals found in radium ore from the Belgian Congo was determined as 206.20 as compared wit,h a control sample of ordinary lead which gave a value of 207.18. Evidently therefore the lead in these minerals consists chiefly of uranium lead; and the minerals must have been formed long after the original deposit of the uraninite. J. F. S.Hardness of Lead-Thallium and Cadmium-Thallium Alloys. C. DI CAPUA (Atti R. Accad. Lincei 1923 [v] 32 ii 343-346).-The thermal diagram obtained by the author for the miscibility gap of the system lead-thallium confirms that given by Lewkonja (A. 1907 ii 261) and by Kurnakov and Pushin (A. 1907 ii 262) the gap extending over the region 6-23% of lead. The hardness diagram resembles the pressure of flow curve for these alloys (cf. Kurnakov and Schemtschuschny A. 1909 ii 855). Thallium increases the hardness of lead to a maximum a t 60-60~o T1 a minimum .being reached at about SOYO which is the saturation point; from 80 to 94% the course of the hardness curve does not correspond with the diagram of state. The hardness of thallium is increased by addition of lead to a maximum corresponding with the formation of saturated mixed crystals of lead in thallium.The hardness diagram for cadmium-thallium alloys agrees well with the fusion diagram and indicates a slight solubility of cadmium in thallium in the solid state. T. H. P. E. ,4. OWEN and G . D. PRESTON (Proc. Physical SOC. 1923,36,14-30).-By X-ray analysis it is established that a distortion of the respective lattices character- ising the atomic structures of solid solutions of copper-aluminium aluminium-magnesium and copper-nickel is produced when a solute atom replaces an atom in the lattice of the solvent. The eutectic alloy of aluminium and copper is shown to consist of CuAl and another substance. CuA1 possesses a simple tetragonal lattice of side 4-28 A. and axial ratio 0.562 whilst the atomic structure of CuAl resembles that of a salid solution of aluminium in copper but the distortion is considerably greater. Instability of Cupric Hydroxide.G. FOWLEY (Chem. News 1924 128 2-5).-The hypothesis of Weiser (A. 1923 ii 566) to account for the stabilising effect of dilute solutions of certain salts such as manganous sulphate on suspensions of gelatinous cupric hydroxide is held to be untenable because other solvents which exert a slight solvent action on cupric hydroxide such as sodium hydroxide accelerate its decomposition. The amounts of added salts were not trifling when their action is considered and varying molecular quantities were required to produce the same effect. Atomic Weight of Lead from the Belgian Congo. X-Ray Analysis of Solid Solutions.J. S. G . T. 5 - 2ii. 112 ABSTRACTS OF CHEMICAL PAPERS. The author adduces experimental evidence to prove that no such continuous solvent action as Weiser imagines can possibly take place. Crystalline varieties of cupric hydroxide on being kept at the ordinary temperature gradually become discoloured the change being first noticeable after about two years. One sample at least twelve years old eventually went quite black. The crystalline hydroxide appears to pass very slowly through those changes which are so rapid in the gelatinous variety that the intermediate stages are not seen. In each case the changes are accelerated by soluble hydroxides. The crystalline variety must therefore be regarded as a highly stable intermediate form in a state of suspended transformation.It is considered that the gelatinous copper hydroxide used by Weiser contained adsorbed or combined sodium hydroxide which was effectively removed by the hot salt solutions added as insoluble basic salts. The stabilisation described therefore consisted in removing a catalyst and in allowing the unstable gelatinous substance safely to pass into the more stable crystalline form. In every case in which stabilisation was successful a substance was added which wculd very thoroughly remove a soluble base. Sodium sulphate and suspensions of colloidal metallic oxides however showed no stabilising power. Chemical Constant of Mercury. F. SIMON (2. physikal. Chem. 1923,107,279-284).-The atomic heat of mercury has been measured a t temperatures betweeen 9' and 14" Abs.and the following values have been obtained 9-78" 1.107; 10.17" 1-151 ; 10.89' 1.244 ; 11-09' 1.284 ; 12-35' 1.443 ; 12-55' 1.482 and 13-35" 1.570. These values are expressed by the equation Cp=$ Debye function (l20)+ Einstein function (25)+21.10-5!PT.:''3. The chemical constant of mercury has been calculated to + 1.950 with a maximum error of O-OSY,. H. C. R. This value is 0.084 larger than the theoretical value. J. F. S. Ebullioscopy of Double Salts of Mercuric Chloride with Alkali Chlorides. P. BOURION and E. ROUYER (Compt. rend. 1924 178 86-88).-The proof (A. 1923 ii 568) that mercuric chloride exists in solution partly as treble molecules is taken into account in connexion with the ebullioscopic determination of the molecular weights of sodium potassium and ammonium mercuri- chlorides (cf.A. 1923 ii 534) which are shown to be of the type MCl,HgCl or M[HgCl,]. If the association of mercuric chloride is ignored the results lead to the formula BMCl,HgCl,. E. E. T. Complex Sulphates of Quadrivalent Cerium and the Position of this Element in the Periodic Classification. V. CUTTICA (Gazzetta 1923 53 761-768).-The formuh of the two cerous-ceric sulphates show that these compounds may be regarded as derivatives of a hypothetical ceri-sulphuric acid H,Ce(SO,) originating from ceric hydroxide by replacement of the four oxygen atoms by four SO radicals. The assumption that this complex acid is present in sulphuric acid solutions of ceric sulphate finds support in the compositions of the double compounds formed by ceric sulphate with sodium and thallous sulphates.No tendencyIN'ORGANIC CHEMISTRY. ii. 113 to unite with ceric sulphate is however observed with lithium sulphate and the double silver compound 10Ce(S0,),,6Ag,S04 is totally different from those given by sodium and thallium. A solution containing bismuth sulphate which is isomorphous with the sulphates of the rare earths deposits according to the conditions one of the three compounds (1) Ce~(S0,),(Ce1=,Bi)H,12H,0 (2) Ce( SO,),,Bi( OH)SO,,SH,O and (3) Ce( S04),,2Bi,( SO,) 15H,O. Compound (1) contains always little bismuth the presence of which is due to the solubility in the solid state of bismuth sulphate in cerous sulphate ; it forms orange bipyramidal prisms belonging to the hexagonal system and similar in every way to those of the acid sulphate Ce1V(S04)4,CeIIIH 12H,O.Compound (2) crystal- lises in long cedar-yellow needles and compound (3) in long yolk-yellow prisms. The question of the position to be assigned to cerium in the periodic system is discussed and it is considered that the weight of the evidence favours the view that this metal belongs to the first sub-group of group IV. That cerium should be placed in the same column as thorium is indicated by the fact that cerium and t'horium sulphates form mixed crystals. As a general rule it is indeed found that isomorphism exists between the salts of the lowest oxide of the heavy metal occupying the lowest position in each group and those of the element of the first sub-group of the preceding group.With organic bases as with silver and bismuth the hypothetical acid H4Ce(S0,) forms double or complex salts with constitutions varying according to the nature of the base. Only with strong bases does normal salification occur. [With L. BONAMICI.]-I~ addition to those described above the following salts have been prepared Ce(S0,),,2Na2SO orange-yellow prismatic crystals ; Ce(S04),,2T1,S0 deep orange-red prismatic crystals ; with guanidine sulphate 2Ce(SO,),NH:C(NH,),,O*5H,SO 10H,O elongated yellow prisms ; Ce2(S04),,5CO(NH,),,H,S0 amher- yellow crystals . T. H. P. Double Sulphites of Cerium Lanthanum and Didymium with the Alkali Elements. V. CUTTICA (Gametta 1923 53 769-772).-According to Grossmann (A 1905 ij 326) the sul- phites of cerium lanthanum and didymium exhibit no tendency to form molecular compounds with sulphites of the alkali metals but the author finds that such double sulphites are readily obtainable under suitable conditions.If excess of an alkali metal sulphite is added to a solution of the hydrogen sulphite of the rare earth metal and the liquid subsequently heated on a water-bath in a flask connected with a water pump so that air is largely excluded the double sulphite separates as a microscopic powder which is highly stable in the air but undergoes gradual oxidation to sulphate if suspended in water. In this way were prepared cerium potassium sulphite Ce2(S0,)3,K,S0,,4H20 ; cerium ammonium sulphite 2Ce,(S0,),,3(NH4)2SO ; 6"ii. 114 ABSTRACTS OF CHEMICAL PAPERS. cerium sodium sulphite Ce( S0,),,Na2S03,2H20 ; lanthanum potassium sulphite 2La2( SO3),,3K2SO,,~H2O ; lanthanum ammonium sulphite La,(SO,) (NH,),S03 ; didymtum potassium sulphite If in the above method of preparation a deficit of sodium sulphite is employed the cerium sodium sulphite 3Ce2(S0,)3,2Na2S0,,2H20 is obtained.T. H. P. Di2( SO,) K2S 0,,4H20. Ternary Alloys of Aluminium Copper and Magnesium. BUNTARO OHTANI ( J . Chem. Ind. Japan 1923 26 427448).- The author has studied that part of the ternary system containing alloys of which the copper content extends up to 13o;d and magnes- ium content to 147;. The liquidus of these alloys is depressed with increasing copper and magnesium content and the liquidus surface of the system slopes downwards from the aluminium corner. The solubility of magnesium and of copper in aluminium decreases according to the increasing content of copper and magnesium respectively.For example in the presence of Syo of magnesium the maximum solubility of copper is reduced from 6% to 374. The alloys of composition within the limit above described form a homogeneous solid solution ( a ) but the alloys of a composition beyond this limit have two arrest-points on these cooling curves and show a duplex structure consisting of a and an eutectic (a+p) on the cooling curve ingot. This eutectic surface slopes downwards from the Al-Cu binary eutectic line to the A1-Mg alloy side. Tensile tests and measurements of Brinell’s hardness and specific gravities on chill and sand castings were applied. The hardness increases slowly with copper content and rapidly with magnesium content within the limit of l:/o magnesium then slowly increases.The specific gravity increases linearly with copper content and decreases linearly with magnesium content. If the ratio of magnesium and copper is 5 6 the specific gravity remains constant. K. K. Manganese Dioxide in the Catalytic Oxidation of Carbon Monoxide. W. A. WHITESELL and J. C. W. FRAZER ( J . Amer. Chem. Xoc. 1923 45 2841-2851).-Manganese dioxide which has a great catalytic activity in the oxidation of carbon monoxide at temperatures as low as -9O” may be prepared (a) by the decom- position of potassium permanganate with concentrated nitric acid ( b ) by treating Prbmy’s oxide with concentrated nitric acid diluting and washing (c) by the oxidation of manganous sulphate with potassium permanganate in nitric acid solution and ( d ) by thc oxidation of precipitated manganous hydroxide.Analytical results show that the amount of impurities such as adsorbed alkali plays an important part in the activity of these catalysts. Experiments show a considerable temperature interval between the points required to oxidise hydrogen and carbon nionoside by these samples of active manganese dioxide. Carbon monoxide adsorbed by nian- ganese dioxide is desorbed as carbon dioxide. It is suggested that the mechanism of the oxidation of carbon monoxide consists in the adsorption and simultaneous Oxidation hy thc manganeseINORGANIC CHEMISTRY. ii. 116 dioxide followed by desorption of the carbon dioxide and re- oxidation of the catalyst.Mechanism of the Reduction of Permanganate and its Physico-chemical Basis. VII. The Reduction of Manganate by Formaldehyde. J. HOLLUTA (2. .;l~ysikuZ. Chem. 1923 107 249-269; cf. A. 1923 ii 864).-A continuation of previous work in which it is shown that the reduction of inanganate by formalde- hyde takes place with the intermediate formation of forinate-ions and consequently is a reaction which takes place in two stages. The order of the reaction has been determined by two methods and the influence of the concentration of the participating species on the velocity of the reaction has been investigated. I n keeping with the theory of successive reactions it ir found that tJhe velocity coefficient of the second order calciilated on the basis of the equation 2Mn0,”+H*CHO=2MnO2+CO,”+2OH’ exhibits a tendency to decrease whilst that calculated on the basis of the equation MnOql’+ H*CHO=MnO,+HCO,’+OH‘ shows a tendency to increase.In consequence of the great difference of velocity of the reduction by formaldehydc and by formates the velocity coefficient calcu- lated on the second equation given above comes very close to the true coefficient. The connexion between the alkalinity of the solution and the velocity coefficient has also been studied and it is found that the latter as a first approximation is inversely propor- tional to the square root of the hydroxyl-ion concentration and also directly proportional to the eighth root of the partial pressure of the oxygen liberated by the manganate. Small divergences from these relationships are explained.The influence of the hydroxyl-ion on the molecular condition of the formaldehyde in its connexion with the reduction of the inanganate is discussed. The mechanism of the reduction is represented by the scheme 2[Mn04”+3H20= Mn(OH),+20H’+ 01 O+H*CHO + OH’=HCO,’+H,O (rapid re- action measured) ; 0 +HCO,’ + OH’ ==CO,” +K,O. Slow Coagulation of Concentrated Ferric Oxide Sols to Reversible Jellies. E. SCHALEK and A. SZEGVARI (KoZZoid Z . 1923 33 326-334).-Concentrated ferric oxide sols set on the addition of definite concentrations of electrolytes to coherent jellies which on shaking become again liquid and then again set; this process may be repeated indefinitely. On changing the con- centration of electrolyte the sol and gel undergo the usual floccu- lation.The time necessary for the re-solidification of the jelly is a reproducible quantity. The velocity of solidification increases rapidly with the temperature and its logarithm is proportional to the temperature ; it also increases rapidly with the concentration of the added electrolyte; the logarithm of the velocity is also pro- portional to the concentration. Consequently the process is to be regarded as a slow coagulation. The solidification process is sensi- tised by alcohol. In comparison with the sol the liquefied gel shows an increased displacement elasticity. Ultramicroscopic examination of the resolidification shows that the particles do not come closer together and there is no formation of secondary particles. Similar J. F.S . J. 3’. S. 5”-2ii. 116 ABSTRACTS OF CHEMICAL PAPERS. results have been obtained with zirconium scandirim and aluminium hydroxide sols and with stannic oxide sols. Pharmacological Investigations on Iron. I. Colloidal Ferrous Sulphide prepared in Presence of Gelatin. L. SABBATANI (Atti R. Accnd. Lincei 1923 [v] 32 ii 326-330).- Colloidal ferrous sulphide solutions prepared from ferrous sulphate and sodium sulphide in presence of gelatin are highly stable and serve well for pharmacological experiments the gelatin and sodium sulphate they contain being without disturbing effect. The most stable and most highly disperse solutions are those containing 0.05 g.-mol. of ferrous sulphide per litre and 5% of gelatin. Such solutions set hard and must be liquefied in warm water and used when tepid; they readily undergo oxidation which may be pre- vented by covering the surface with a layer of vaselin oil or better paraffin wax.If great care is taken they withstand sterilisation in steam and they may be diluted with water which has been thoroughly boiled and then cooled. Oxidation which is facilitated by heating or diluting the solutions proceeds in accordance with the equation 2FeS + 3 0 =Fe,O3+S2. T. H. P. Double Halides of Cobalt Bases. F. EPHRAIM and P. MOSIMANN (Helv. Chim. Acta 1923 6 1112-1132).-The halides of cobaltammine bases do not form double salts with other halides with such readiness as was expected. As far as could be ascertained double salts were only formed with salts of zinc cadmium mercury and lead and in the case of luteo-salts with antimony and bismuth trichlorides.In the case of both luteo- and roseo-salts zinc forms a double chloride cadmium a chloride and bromide and mercury a chloride bromide and iodide; there is thus a diminishing tendency to form double salts as the atomic weight of the halogen increases. Flavo-salts and croceo-salts do riot form double salts with zinc but both do so with mercury and thc flavo-salts form a double chloride and bromide but not an iodide with cadmium salts The complexity of the salts increases with the atomic weight of the heavy metal; thus the luteo-chloride combines with lZnCl 2CdC12 3HgCl or 4PbC1,. The following new compounds are described Luteo-salts.-Two hc~arnmi?zecobalti-cadmium chlorides were obtained both microcrystalline powders [Co (NH,) 6]c137 2CdC1,,31-120 and [ Co (NH3)6]C'j,,CdC1,,H20 ; the double bromide [Co(NH3),]Br,,3CdBr2,3H20 forms very thin flat rectangular tablets.Hexamminecobalti-zinc chloride [Co(NH,),]C1,,ZnC12,H,? forms lustrous apparently hexagonal prisms. Two hexamm%necobalti-mercuric bromides were obtained [Co (NH,) 6]Br3,3HgRr microscopic needles and glistening rectangular leaflets. The iodide corresponding with the second bromidc has been previously described; there was also obtained [ Co (NH,) 6]13. 3Hg12 6H20 in well-f ormed microscopic crystals. J. F. S. [Co(~'H,),]Br,,HgBr A cklorocyanvde of the composition 2[Co(NH3) JC13 5Hg (CN)z,H,O,INORGANIC CREMISTRY. ii. 117 forming glistening six-sided leaflets was also obtained. Two hexamminecobalti-lead chlorides were obtained ; forms long hairy needles and [CO(NH,)~]C~~,~P~C~ extremely thin six-sided leaflets showing all colours.Three bromides are described [Co(NH,),]Br,,4PbBr2,2H2O forms glistening four-sided leaflets ; ~ [ C O ( N H ) ~ ] B ~ ~ P ~ B ~ ~ forms long glistening orange- brown needles and [Co(NH,),]Br,,PbBr needles. Ilexammine- cobalti-antimony chloride [CO(NH,)~]C~~,S~C~,,H,O forms a pale yellow precipitate ; the bismuth compound is similar but anhydrous. Roseo-salts.-The composition of aquopentamminecobalti-zinc chloride is doubtful but approximates to [CO(NH,)~H,O]C~,,Z~C~~. The cadmium salt aggregates of red microscopic prisms has the composition [Co( NH,)~5H,0]C1,,2CdC1 3H20. The double bromide forms dark red glistenlng plates ~[CO(NH,)~H,O]B~,,~C~E~,.Two aquopentamminecobalti-mercuric bromides were obfamed bright red microscopic star-shaped aggregates of needles and [Co(NH3),HzO]Br3,3HgBr fine needles or a dull rose crystalline powder. The corresponding iodide appears to contain Co Hg= 1 1. Flavo- and croceo-salts.-trans-Dinitrotetrammine( croceo)cobalti- mercuric chloride forms yellow microscopic four-sided plates or needles [CO(NH,),(NO~)~]C~,~H~C~~,~H,O. Two mercuric chlorides of the flavo-(cis)series were obtained [Co(NH,),(N02),]C1,2HgC1 long yellowish- brown needles and 2[ Co ( NHp)4(N02)2]Cl,HgCl similar crystals. Similarly one double bromide of the trans- series was obtained 2[Co(NH3),( N0,),]Br,3HgBr2 microscopic rectangular leaflets and two of the cis-series felted microscopic yellow needles and the second containing potassium bromide ~[CO(NH~)~(NO~),]B~,H~B~~,KB~ needles.The double iodide of the croceo-series forms dask yellow six-sided tablets Co Hg=3 2 and of the flavo-series bright yellow needles of the same composition. cis-Dinitrotetrammine(flaz.o)cobalti- cadmium chloride [CO(NH,),(NO,)]C~,C~C~~ forms fine bundles of needles and the corresponding bromide Co Cd=2 1 long brown needles. Corresponding croceo-cadmium salts were not obtained. [Co(NH3)61C13,PbC1~ [Co(NH3)5HzOIBr3 HgBr [Co(NH,),(NO,),IBr,2HgBr E. H. R. Molybdovanado-arsenates and Tungstovanado-arsenates (Hetero-tri-arsenates). G. CANNERI (Gazxetta 1923 53 773- 778).-The compounds here described have been prepared by the following methods the solutions in all cases being kept acid (1) By means of solutions containing a small proportion of an arsenate together with vanadic and molybdic (or tungstic) acids ; (2) by addition of vanadic anhydride to solutions of molybdo- arsenates or tungsto-arsenates; (3) by addition of arsenic acid to solutions containing molybdates (or tungstates) and vanadates.The composition of the complex compound varies with the con- centration and acidity of the solution.li. 118 ARSTRSCTS OF CHEMICAL PAPERS. The variety of the ratios in which combination occurs between the constituent oxides in these compounds would appear to indicate that many of the compounds are mere isomorphous mixtures of far simpler true compounds. On the other hand however from the very small and but slightly variable proportions of arsenic present it may be assumed that the miscibility is effected between groupings of which the arsenic constitutes the central nucleus.The typical heterotri-arsenates may thus be represented by the annexed scheme in which R' represents R ' P S ( ~ ~ ~ ? ~ ~ ) ' ]nH20 six (three) atoms of an alkali (alkaline- (R 207)Y earth) metal R" vanadium and R"' molybdenum or tungsten. Only in certain cases do the salts now described approximate to this hypothetical scheme. Analysis of these compounds presents difficulties means for over- coming which are described (cf. Friedheim Decker and Diem X. 1905 ii 764). Three ammonium arsenomolybdo~anadates have been prepared 6(NH,),0,As20,,l 1Mo0,,5V205,50H,0 an orange-yellow micro- crystalline precipitate ; 5 (NH,),O As,O ,,20Mo 0 3V,O ,,50H,O a yellow microcrystalline precipitate ; 11 (NH,)20,~As,05,25M003,4V205,96H,0 a red powder.Two barzum arsenomolybdocanadates 15Ba0,As,0,,26M00,,3V~05,62H,0 and 7Ba0,As205,33M003,4V,0,,34H,0 a yellow precipitate. Thall- ium arsenomolybdoranadate 3T1,0,As20,,32M00,,5V205,45H,0 forms a yellow precipitate ; ammonium arsenotungstocanadate 1 8(NH,),0,As,05,2 1 W 0,,4V205 13H,O red prismatic crystals ; thallium arsenot ungstocanadate 6T1,O,As2O5,2 1 W O,,5V,O5 1 3H,O a red powder ; and barium arsenotungstocanadate 6Ba0,As,05 17WO,,Ci~V,O,,40HZ0 small blood-red octahedra. T. H. P. Molybdovanadates. G. CANKERI (G'axxetta 1923 53 779- 794) .-The composition of the molybdovanadahes varies with the conditions under which they are formed particularly with the acidity of the medium and with the temperature of crystallisation.The author finds that the electrical conductivity a t 30" of solutions of sodium metavanadate acidified with increasing proportions of acetic acid varies continuously the condensation of the molecules of vanadic acid being thus a continuous function of the concentra- tion of the acetic acid; a t tlhe same time the colour changes gradually from yellow to orange-red. In view of the fact that dissolution of molybdic anhydride in solutions of metavanadates constitutes a met'hod of preparing the molybdovanadates the author has commenced an investigation into the systems NH4V0 MOO KVO MOO and NaVO MOO at different temperatures. The results a t present available show that within the limits imposed by the value of the solubility of molybdic anhydride in solutions of the metavanadates compounds of two types differing sharply in their physical properties are formed. These crystalhe respectively in large orange-red prisms,INORGANIC CHEMISTRY.ii. 119 and in yellow silky needles or sometimes in pulverulent form. One and the same solution may give both red and yellow crystals either together or successively in either order. The value of the ratio V,O MOO varies gradually in the red crystals from 3 1 to values corresponding with the maximum percentage of vanadium this approaching the proportion occurring in polyvanadates. The ratio changes suddenly in value for the yellow crystals which are poorer in vanadium. The various red crystals appear to consist of isomorphous mix- tures but the isomorphogenous terms cannot yet be defined neither can their chemical natures be established ; it is however possible that they consist of polyvanadates and polymolybdates.Along with these isomorphous mixtures there exist certain well-defined compounds which are obtained under definite conditions. With these com- pounds difliculty is encountered in distinguishing between combined water and water of crystallisation but the author regards them as heteropolyaquates and ascribes to them formulae based on the hypothesis of Rosenheim (A. 1911 i 109 265 ; ii 116 612 ; 1913 ii 59) and of Miolati and Pizzighelli (A. 1908 ii 595) to which preference is to be accorded over Prandtl's views (A. 1913 ii 61). according to the latter the molybdovanadates are double salts and should hence be completely dissociated in solution ; in sufficiently dilute solution therefore fractional precipitation of the dif€erent constituents should be possible but this is not found to be the case.w i t h R. RAGIONIERI.]-T~~ red crystals formed by the system NH,,VO MOO have the same colour and crystalline habit in all cases. The pale yellow silky crystals consist of the compound 4(NH,)20,5M00,,3V20,,10H20. The guanidine compound pre- pared from the latter has the composition 3 (CH6N,),0,4M00,,4V,0 10H20. w i t h G. WINSPEARE.]-T~~ pale yellow crystals formed by the system KVO,:MoO at 30" vary in composition according to the concentration of the solution; compounds of the formulz 4K,0,4M00,,3V205 7H,O and 3K,O 6Mo O SV,O 7H20 were separated.[With c. DELLA PERcoLA.']-In the system NaVO Moo the compound 4Na20,8M00,,3V205 10H20 occurs in equilibrium with the red mixed crystals until the molybdenum is increased to make the ratio V,O MoO,=l 2 and separates as a single pure phase when the molybdenum is still further increased in amount. The red salt 2Na20,Mo0,,3V,05,9H,0 yields the barium compound 3Ba0,Mo03,4V205 12H20 and the red salt 3Na20,2M00,,3V,05 1 2H20 the guanidine compound 3(CH6N,),O,N1oO3,V,O5. T. H. P. Electrolytic Preparation of Antimony-Copper and Antimony-Bismuth Alloys. A. MAZZUCCHELLI and L. TONINI (Atti R. Accad. Lincei 1923 [v] 32 ji 290-292).-Electrolysis of a hydrochloric acid solution of a mixture of antimony and copper the latter constituting 20-50% of the total dissolvedii.120 ABSTRACTS OF CHEMICAL PAPERS. metal results in a homogeneous brittle violet deposit containing a small proportion of antimony trichloride (cf. Mazzucchelli A. 1915 ii 19) and copper and antimony approximately in the propor- tions corresponding with the compound Cu,Sb. When the dissolved metal contains about 90% of copper the deposit formed is graphite- grey and highly brittle and contains a little antimony trichloride together with rather more copper and rather less antimony than the formula C'u,S b requires. Similar experiments with hydrochloric acid solutioiis of antimony and bismuth yield extremely brittle deposits containing the two metals in proportions varying in the same sense as the compositions of the original solutions.H. FREUNDLICH and 13. BAERW~ND (Kolloid Z . 1923 33,275-279).-The properties of the sol produced by shaking hydrated osmium dioxide with water have been investigated. It! is shown that the colloidal particles are negatively charged and migrate to the anode. The sol in its behaviour to electrolytes shows the behaviour typical of negatively charged sols that is the kation of the precipitating electrolyte is determinative of the action of the electrolyte. The precipitation values are in keeping with the valency rule. Observation of the sol by means of an ultramicroscope shows that the particles are not spherical. The addition of gelatin to osmium dioxide sols at first brings about coagulation which is followed by a protective action. In keeping with this it is found that on the addition of electrolytes gelatin exercises both a sensitising and a protective actian. The so1 is not coagulated at any concentrations by tannin and saponin. The migration velocity of osmium dioxide sols on the addition of gelatin increases almost up to the coagulating concentration ; it then falls and finally increases but there is no reversal of the charge of the sol. The osmium dioxide sol as such has no decomposing action on formic acid a t loo" but it is reduced to the metal sol and this brings about a rapid decomposition of the acid. 5. F. S. T. H. P. Some Properties of Osmium Dioxide Sol. Mineralogical Chemistry. Chalcophyllite from Chile. E. V. SHANNON (,4mer. J . Sci. 1924 [v] 7 31-36).-Emerald-green crusts of minute platy crystals from the Teniente copper mine near Rancagua gave CuO. Also,. As,O,. P,O,. SO,. SiO,. H,O(at 110'). H,O(over 110"). Total. 46.54 3.49 13.23 0.67 6.67 1-33 14.40 14-04 100.37 corresponding with 4Cu0 ~Al,O,,~As,O SO,,lOH,O. The refrac- tive indices of fresh material are ~=1*552 w = 1 . 6 1 8 ; these change when the material is exposed to air owing to loss of water ; and for material dried a t 110" they arc E-1.618 0=1.680. L. J . s.