Vapour Density, determination

Vapour density determinations show that paraldehyde is formed by the union of three molecules of acetaldehyde. Since the substance has no aldehydic properties the following structure, that of a cyclic triacetal, is properly given to it ... 

T. E. Thorpe s formula for the specific volume i> at the temp. 0 is u=l +00009158960 +0 0000008329602 +0 00000000275O03. The vapour density is that theoretically required for IC1 with oxygen 32, the value for IC1 is 162 38 at 120°, the vapour density is 1606, and at 512°. 156 4. Conclusions as to the degree of dissociation at different temp, cannot be derived from the vapour density determinations since it proceeds without changing the number of molecules—2ICI—>I2+C12- Iodine trichloride vapour is almost completely dissociated into the monochloride and chlorine. K. Beck s value for the viscosity is 7 029 at 15°, 5 069 at 28 4°—benzene at 5° unity. 

On elimination of sulphur from hydrogen sulphide an equal volume of hydrogen remains, which of course is evidence for the composition represented by the formula H S. Vapour density determinations also show that the gas consists of single H2S molecules,1 a value 34-085 2 having been obtained for the molecular weight, after making due corrections to the vapour density result. In the liquid state also there appears to be no association of the molecules and the molecular formula is still H2S. 

When passed through a red-hot tube the vapour is almost entirely decomposed into sulphur dioxide, sulphur trioxide and chlorine. Vapour density determinations at various temperatures, and analyses of the decomposition products, indicate that decomposition proceeds according to the equations 8... 

Carbon disulphide vapour appears to be associated to a small extent. When the vapour and ether vapour are mixed at constant volume at 80° C. under atmospheric pressure, the increase of pressure observed indicates previous association of the carbon disulphide to the extent of 0-14 per cent., whilst vapour density determinations by Dumas method give results corresponding with 2 per cent, association.3... 

The maximum absorption of light 4 by selenium vapour occurs between 650° and 700° C., and vapour density determinations show that the average molecular weight at this temperature corresponds to Se3. 

Vapour density determinations show that tellurium is diatomic at high temperatures (about 1500° C.),5 whilst at 2100° C. considerable dissociation into single atoms has taken place. According to Jouniaux 6 the element is monatomic at 357° C. At lower temperatures, as in the case of sulphur and selenium, the molecule is more complex. The vapour pressure of tellurium has been determined 7 and is as follows ... 

Arsenious oxide is not appreciably volatile at ordinary temperatures,2 but vapour is emitted at 100° C.3 Vapour density determinations 4 indicate that at lower temperatures the molecules are mainly As4Oe but, as the temperature rises, dissociation occurs, which is appreciable at 850° C. and practically complete at 1800° C., simple As203 molecules being formed. The following values for the vapour density (Theory As406 = 13-76) were obtained by Biltz 5... 

Messinger 1 who, from vapour density determinations, concluded that the vapour of the disulphide was considerably associated. The sublimation curves do not show any indication of the formation of a pentasulphide. 

The next member of the series, tetraphosphonitrilic chloride, P4N4GT8, forms colourless prisms with a sp. gr. 2-18. B. Schenck and G. Bomer gave 185° for the b.p. at 10 mm. press., and 123-5° for the m.p., and added that above 255° it behaves like the tri-polymer. H, N. Stokes found that analyses, vapour density determinations in dry hydrogen, and the depression of the f.p. of benzene soln., agree with the formula P4N4C18 and by analogy with triphosphonitrilic chloride, the constitution may be ... 

The chemical properties Of phosphine.—H. Davy10 analyzed the gas, but his sample must have been mixed with so much hydrogen as to render his result useless for determining the composition of the gas. The analyses of H. Rose, J. B. A. Dumas, and U. J. J. Leverrier agree with the empirical formula PH3 and the vapour density determinations previously indicated show that this is also the mol. formula. A. O. Rankine discussed the structure of the molecules of the family of trihydrides H. Remy, and H. Henstock, the electronic structure and G. W. F. Holroyd gave... 

Properties.—Thiophosphoryl chloride is a transparent colourless liquid which fumes in the air and smells of hydrogen sulphide. The formula has been established by analysis and vapour density determination. The density of the liquid is 1-66820 at 0° C. and 1-45.599 at the normal boiling-point, 125-12° C.8 The coefficient of expansion between these temperatures is given by8... 

Aluminium tri-isoamyl is a liquid, boiling about 250" C. at 80 to 100 mm. vapour density determinations indicate the formula to be... 

Vapour-density Determination at Very High Temperatures.—Victor Meyer was able to extend up to 1700° the method of air displacement discovered by him, and thus to... 

According to Piccard, the principal constituent is a hydrocarbon of the empirical formula (C Hg)x, which from a vapour density determination appears to be CjcH,. 

Analysis of Binary Mixtures.—A useful application of vapour density determinations is to the analysis of binary mixtures of (normal) liquids, the vapour density of which is known. W nj Vi... 

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