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the periodic acid, then the time t = k(C,C,)", where calculated from two consecutive observations, z= log t- log t If the log (CC), log (C,C,) sulphurous acid be kept constant in amount, and the periodic acid. allowed to vary, t = k/Cp, where k is constant and У calculated from
two consecutive observation
log C",log C
Influence of Molecular Contiguity on the Chemical Equilibrium of Homogeneous Gaseous Systems. By SARRAU and VIEILLE (Compt. rend., 105, 1222-1224).-The combustion of organic compounds which do not contain sufficient oxygen for complete oxidation results in the production of a condition of equilibrium between the gaseous products, some of which are completely oxidised, as carbonic anhydride and water, whilst in others, such as carbonic oxide, hydrogen, and methane, oxidation is incomplete. Experiment shows that the conditions of final equilibrium change with an increase in the weight of substance exploded in the same space, that is to say, with an increase in the pressure produced by the products. Two principal reactions are concerned in the progressive alteration of equilibrium. The first CO + H2O = CO2 + H2, usually occurs; the second, 2CO + 2H2O = CO2 + CH,, takes place when the first has reduced the proportion of water vapour and increased the proportion of free hydrogen to a certain extent, or when the explosive contains so little oxygen that water is formed in relatively very small quantity. The first reaction was observed to take place by Noble and Abel in their experiments with gunpowder. The authors find that it also takes place in the explosion of cotton powder and of picrates. The results obtained with cotton powder, C2H29N11O2, are as follows:
0.010 33CO + 15CO2 + 8H2 + 11N2 + 21H2O 30CO +18CO2+ 11H2+ 11N2+ 18H2O 27CO + 21CO2 + 14H2 + 11N2 + 15H2O 26CO22CO, + 15H, + 11N2+ 14H2O
The temperature of final equilibrium is about 3000°, the pressure varying between 100 and 4000 atmospheres. The formation of methane, which occurs only to a very limited extent in the case of cotton powder, becomes more marked with such compounds as the lower nitrated derivatives, picrates, and picric acid. The results with the last compound were as follows:
11CO2 + 84CO + 24N1⁄2 + CH + 16H, + 6H,O 20CO2 + 69CO + 24N2 + 7CH, + 7H2 + 3H2O 25C061CO + 24N2+94CH, + 4H2+ H2O+C.
The pressures varied from 1000 to 7500 atmos. The reactions which tend to reduce the proportion of carbonic oxide are exothermic.
In the case of the first reaction, the development of heat is not great, and there is no alteration in the volume of the gas; but in the second case there is a considerable development of heat, and the volume of the gases taking part in the change is reduced to one-half. The alterations in the conditions of equilibrium tend towards the development of the maximum quantity of heat, and the two reactions concur in making the pressure increase in a greater ratio than the weight of the explosive charge. C. H. B.
Influence of Neutral Salts on the Rate of Hydrolysis of Ethyl Acetate. By S. ARRHENIUS (Zeit. physikal. Chem., 1, 110-133).— In Warder and Reicher's equation for the rate of saponification, dC = kCC1, where t is the time, C the concentration of the base, and C, that of the salt, k is a quantity which the author proposes to call the specific rate of saponification. This quantity is independent of the amounts of base and salt which act on one another, but most probably varies for different concentrations. In the present case, the influence of the presence of neutral salts on k was studied. This influence is as a rule small, and k remains nearly constant; salts of the halogens and nitrates lower, whilst sulphates and hyposulphites raise the value of k. The influence of potassium iodide is greater than that of potassium bromide, which is greater than that of potassium chloride, the three being very nearly in the ratio 3 : 2 : 1.
Quite abnormal is the influence of ammonia and ammonium salts, the action being very great and varying very distinctly with the amount of salt in solution. k in fact here depends on the amount of dissolved salt, S, according to the equation k =
1 + aS+ bS2
The rate of hydrolysis is practically in all cases proportional to the conductivity. The low conductivity of a weak base such as ammonia, on which other dissolved electrolytes can exercise such a large relative influence, probably explains its abnormal behaviour.
Formation and Decomposition of Ethereal Salts: Decomposition of Liquid Tertiary Amyl Acetate. By D. KONOWALOFF (Zeit. physikal. Chem., 1, 63-67).-Menschutkin (Abstr., 1883, 178, 309) has observed that the rate of decomposition of liquid tertiary amyl acetate at 180° increases until about 50 per cent. of the acetate employed is decomposed, then diminishes, and finally ceases when the decomposition has reached 97.42 per cent. The author shows that the cause of this is the action of the liberated acetic acid on the acetate, and finds that the addition of acetic acid brings about the decomposition of the acetate. By heating amyl acetate with varying amounts of acetic acid for one hour at 159°, he shows that the amount decomposed is dependent on the amount of acetic acid added. This is expressed by the equation d.c/dt = k (100 — x) (x + 24p), where a is the percentage of acetate decomposed in the time t, p the quantity of acetic acid added, 2 the ratio of the molecular weights of the acetate and acetic acid, and k a constant. All other acids have an
action similar to this of acetic acid although in different degree, propionic and butyric acids being far less active.
The action of the haloïd hydrogen acids was also studied, but in these cases the gaseous acid was passed into the liquid acetate at the ordinary temperature. The action is violent, a considerable development of heat takes place, and a tertiary amyl haloïd salt and acetic acid are formed. In the action of hydrogen chloride two stages may be distinguished, the acetate being first decomposed into amylene and acetic acid, and the amylene then combining with the hydrogen chloride. This reaction the author proposes to employ to determine the heat-change represented by C2H1 C2H2O2 = C2H10 + C2H,O2. The comparative ease with which the halogen acids act on tertiary amyl acetate explains the formation of amyl chloride instead of acetate when dimethyl ethyl carbinol is treated with acetic chloride.
Chemical Decomposition produced by Pressure. By W. SPRING and J. H. VAN'T HOFF (Zeit. physikal. Chem., 1, 227-230).The results of numerous experiments show that in many cases substances which exert no action on each other at atmospheric pressure under ordinary circumstances, can be made to combine more or less completely if they are subjected to a pressure sufficient to cause a perceptible condensation. The researches hitherto made relate to compounds, the volume of which is smaller than that of their constituents. It is therefore a question of some interest and importance to examine whether the temperature of conversion can be lowered in the case of copper calcium acetate, for which the volume is greater than that of its constituents.
In the first experiment the acetate finely powdered at a temperature of 16° was submitted to a pressure of 6000 atmospheres. powder was thus reduced to a crystalline mass resembling marble, but presenting no sign of chemical decomposition. Next a screw press (Bull. Acc. Belg., 49, 344) was employed; at a temperature of 40° there were very marked results; three-fourths of the mass being liquefied. On removing the pressure, it became solid again, but the sides of the containing vessel were covered with a coating of copper, and it was possible to pick small leaves of copper out of the mass. The dark blue of the acetate had changed for the most part to green interspersed with white points, showing that the mass had been decomposed into acetate of copper and acetate of calcium. The result was entirely due to the change of volume, since the thermal effect of compression was less than a rise of 1°. When the temperature was raised to 50°, the piston sank without resistance through the mass. The first experiment, which had given a nugatory result, was now repeated in order to discover whether sufficient pressure had been used, or the result had escaped observation. A press worked by a lever was used, and this time it was found that the piston sank 1-25 mm. in an hour, or, roughly, that the whole could be decomposed in about 110 hours. Lastly, potassium sulphate under the same conditions gave no perceptible diminution of volume. Thus, the higher the pressure and temperature, the more quickly is the acetate decomposed. Since the progress of chemical action depends on the time, it
seems that it is not sufficient to say that the molecules of a substance assume the arrangement which corresponds with the given volume directly it is reached, for a substance can be compressed without altering its state, if the pressure does not last too long.
Crystallisation of Mixtures. By O. LEHMANN (Zeit. physikal. Chem., 1, 15-26 and 49-60).-The author discusses the different cases in which mixed crystals have been formed, and the possibility of obtaining such from non-isomorphous forms. He repeats the experiments of Herrmann (Abstr., 1886, 972), on the crystallisation of ethyl quinonedihydroparadicarboxylate with ethyl succinosuccinate with similar results. He also investigates the mixed crystals of ethyl dihydroxyquinoneparadicarboxylate with ethyl tetrahydroxybenzeneparadicarboxylate, and of each of these with each of the two foregoing. These substances, although having a somewhat analogous chemical constitution, differ pretty widely in crystalline form. They give, however, well-defined mixed crystals of form and colour intermediate between those of the two substances of which they are formed.
Constitution of Solutions. By F. RÜDORFF (Ber., 21, 4—11). -Numerous experimenters have found that the solution of a double salt diffuses as if it were a solution of a mixture of its component parts; for this and other reasons, it is generally stated that double salts do not exist as such in solution.
On dialysing solutions of the following double salts, K2SO,,NISO, + 6H2O; K2SO,,MnSO, + 6H2O; (NH1)2SO,,MnSO、 + 6H ̧0; K,SO,,Cr,(SO,) + 24H,0; 2KCl,CuCl + 2H,0; 2NH,C,CuCl + 2H,O; 2KCl,ZnCl2 + H2O; KCl,MgCl2 + 6H2O; 2NaCl,CaCl, + 3H20; BaCl2, CdCl2 + 4H2O, it was found that the ratio of the metals in the dialysate was entirely different from that in the original liquid; the component parts, therefore, do not form a molecular compound, but exist in solution independently of each other. On the other hand, the following double salts, KCN, AgCN; 2KCN, Hg(CN)2; 2KCN, Cd(CN)2; 2KCN,Ni(CN)2; 6KCN,Cu2(CN)2; 2NaCl,PtCl + 6H0; 3NaC2O1, Fe2(C2O1); + 6H2O; 3K,C,O1,Fe2(C2O4)3 + H2O; 3K2C2O1,Cr2(C2O4)3 + 6H2O; are not decomposed, but must exist in solution and diffuse as such, inasmuch as the ratio of the metals is found to be the same in the dialysate as in the original liquid.
Several simultaneous experiments were made with each salt, and a membrane prepared from the cuticle of the cæcum of an ox was found to be most suitable, a parchment membrane not being sufficiently homogeneous. F. S. K.
Absorption of Gases by Petroleum. By S. GNIEWOSZ and A. WALFISZ (Zeit. physikal. Chem., 1, 70-72).-The statement that a layer of petroleum will protect an aqueous solution from the action of the air has led the authors to examine the absorption of oxygen and other gases by Russian petroleum. The following table contains. the results:
The ratio is given on account of E. Wiedemann's statement that the changes which the absorption coefficients of different gases undergo with change of temperature is about the same for all gases; the values for water are given for the sake of comparison. It will be seen that the absorption of oxygen is greater for petroleum than for water, so that the protective action above spoken of must be a doubtful one.
Lecture Experiments with Nitrogen Chloride. By V. MEYER (Ber., 21, 26-28).-An experiment is described by which the explosion of nitrogen chloride can be shown, without danger, by allowing turpentine to come into contact with a few drops of the chloride swimming on the surface of the electrolysed ammonium chloride solution contained in an inverted flask, the whole apparatus being placed under a thick glass case. F. S. K.
Specific Gravity of Sulphuric Acid Solutions. By D. MENDELEEFF (Zeit. physikal. Chem., 1, 273-234).-The composition of the solutions is expressible by the formula H2SO, + mН¿0; p denotes the percentage of H2SO, in the solution, taking S = 32, O = 16, and s is its specific gravity. A table of the value of s derived from the researches of seven experimenters is given for different values of m. Plotting a curve, abscissæ representing the values of p, ordinates those of ds/dp, it appears that the curve consists of a number of straight lines, the discontinuities corresponding with the known hydrates. Since ds/dp is a linear function of p, an integration shows that s is a rational function of p of the second degree, the constants remaining unchanged between two consecutive discontinuities or two consecutive hydrates.
Thus for the values m = 0, 1, 2, 6, 150, there are discontinuities in the values of ds/dp, the first being the most considerable. The data