Slightly soluble

The hydrocarbons are in general only slightly soluble in water. The solubility depends especially on the chemical nature of the hydrocarbons. 

If the spreading is into a limited surface area, as in a laboratory experiment, the film front rather quickly reaches the boundaries of the trough. The film pressure at this stage is low, and the now essentially uniform film more slowly increases in v to the final equilibrium value. The rate of this second-stage process is mainly determined by the rate of release of material from the source, for example a crystal, and the surface concentration F [46]. Franses and co-workers [47] found that the rate of dissolution of hexadecanol particles sprinkled at the water surface controlled the increase in surface pressure here the slight solubility of hexadecanol in the bulk plays a role. 

Lead dioxide is slightly soluble in concentrated nitric acid and concentrated sulphuric acid, and it dissolves in fused alkalis. It therefore has amphoteric properties, although these are not well characteri.sed since it is relatively inert. 

It is slightly soluble in water, giving a neutral solution. It is chemically unreactive and is not easily oxidised or reduced and at room temperature it does not react with hydrogen, halogens, ozone or alkali metals. However, it decomposes into its elements on heating, the decomposition being exothermic ... 

Arsenic(III) oxide is slightly soluble in water, giving a solution with a sweetish taste—but as little as 0.1 g can be a fatal dose (The antidote is freshly-precipitated iron(III) hydroxide.) The solution has an acid reaction to litmus, due to the formation of arsenic(III) acid ... 

When sulphur is melted viscosity changes occur as the temperature is raised. These changes are due to the formation of long-chain polymers (in very pure sulphur, chains containing about 100 (X)0 atoms may be formed). The polymeric nature of molten sulphur can be recognised if molten sulphur is poured in a thin stream into cold water, when a plastic rubbery mass known as plastic sulphur is obtained. This is only slightly soluble in carbon disulphide, but on standing it loses its plasticity and reverts to the soluble rhombic form. If certain substances, for example iodine or oxides of arsenic, are incorporated into the plastic sulphur, the rubbery character can be preserved. 

Hydrogen sulphide is slightly soluble in water, giving an approximately 0.1 M solution under 1 atmosphere pressure it can be removed from the solution by boiling. The solution is weakly acidic and dissolves in alkalis to give sulphides and hydrogensulphides. The equilibrium constants... 

Tellurium dioxide, Te02, is a white non-volatile solid obtained when tellurium is burnt in air. It is only slightly soluble in water but dissolves in alkalis to form salts. 

In its chemistry, cadmium exhibits exclusively the oxidation state + 2 in both ionic and covalent compounds. The hydroxide is soluble in acids to give cadmium(II) salts, and slightly soluble in concentrated alkali where hydroxocadmiates are probably formed it is therefore slightly amphoteric. It is also soluble in ammonia to give ammines, for example Of the halides, cadmium-... 

Lead formate is only slightly soluble in cold water, and insoluble in hot absolute ethanol it can therefore be readily distinguished from lead acetate or sugar of lead because, quite apart from chemical tests, the acetate is readily soluble in cold water and moderately soluble in ethanol. 

Reactions of Nitromethane. (1) Nitromethane, although only slightly soluble in cold water, is freely soluble in sodium hydroxide solution, the alkaline solution slowly becoming yellow in colour. 

Glucosazone is only slightly soluble in boiling ethanol or methylated spirit for recrystallisation therefore it is sufficient to place about 0 5 g. of the crude material in a 150 ml. flask fitted... 

Dissolve 0 5 ml. of glycerol in 20 ml. of w ater, and add 20 ml. of the above 5% aqueous sodium periodate solution. After 15-20 minutes add 12 ml. of the above 10% ethanolic dimedone solution, and stir well at intervals for another 15 minutes. The addition of the dimedone solution may cause a rapid precipitation of some of the dimedone itself, which is only slightly soluble in water, whereas the formaldehyde-dimedone compound separates more slowly from the solution. 

Ethyl acetoacetate is a colourless liquid, d, i 03, slightly soluble in water, but almost insoluble in brine. It has a faint but pleasant odour. It is widely used in chemical syntheses. 

These chlorozincates must not be confused with the non-ionic compounds which quinoline and aniline bases give with neutral zinc chloride the latter have the formulae [(C,H7N)2ZnClt] and [(C,H7N)tZnCl ] respectively, and both are only slightly soluble in water. 

Physical Properties. All colourless liquids, completely miscible with water, except benzyl alcohol and cyclohexanol, which are slightly soluble. Pure glycol and glycerol have high viscosity, which falls as the hygroscopic liquids absorb water from the air. 

Acetaldehyde, CH3CHO, b.p. 21°, is generally used in aqueous solution, which has also a characteristic odour paraldehyde, (CH3CHO)3, is a liquid polymer, b.p. 124°, slightly soluble in water, odour similar to that of acetaldehyde, but less intense. Chloral, CCI3CHO, a liquid, is almost invariably encountered as the stable solid hydrate , CCl3CH(OH)2, m.p. 57 . Both have a characteristic odour the hydrate is readily soluble in water. 

Physical properties. Acetic anhydride, (CH3C0).20, is a colourless liquid with a sharp pungent odour, decomposed slowly by water, in which it is only slightly soluble. 

Naphthalene, CioHs, colourless solid, m.p. 80°, insoluble in water, soluble in alcohol, characteristic odour. Anthracene, CjH4 C2H2 CjH4, m.p. 216°, white crystals when pure, with a faint blue fluorescence, but often very pale yellow crystals insoluble in water, slightly soluble in alcohol. Phenanthrene, m.p. 98°, and biphenyl, m.p. 69°, are white solids. 

The method is used to determine the molecular weight primarily of those compounds which are too slightly soluble in the usual cold solvents for the more efficient freezing-point method to be nployed. 

There appear to be at least two zinc chloride complexes of pyridine, one of m.p. 207 and composition 2CsH,N,ZnCh, sind the other of m.p. 152° and probable composition 2C,H,N,ZnClt,HCl. The former is slightly soluble in water and in hot ethyl alcohol the latter passes into the former in aqueous solution, is readily soluble in hot absolute ethanol and can therefore be readily recrystaUised from this solvent. 

Higher alcohols (> C3) react comparatively slowly with sodium because of the slight solubility of the sodium alkoxide in the alcohol a large excess (say, 8 mols) is therefore employed. The mixed ether is distilled off, and the process (formation of alkoxide and its reaction with the alkyl halide) may be repeated several times. The excess of alcohol can be recovered. cj/cloAliphatic alcohols form sodio compounds with difficulty if small pieces... 

An alternative method for isolating the n-butyl ether utilises the fact that n-butyl alcohol is soluble in saturated calcium chloride solution whilst n-butyl ether is slightly soluble. Cool the reaction mixture in ice and transfer to a separatory fimnel. Wash cautiously with 100 ml. of 2-5-3N sodium hydroxide solution the washings should be alkaline to litmus. Then wash with 30 ml. of water, followed by 30 ml. of saturated calcium chloride solution. Dry with 2-3 g. of anhydrous calcium chloride, filter and distil. Collect the di-n-butyl ether at 139-142°. The yield is 20 g. 

This separation utilises the fact that n-butyl alcohol is soluble in 50 per cent, sulphuric acid by weight, whilst n-butyl ether is only slightly soluble. 

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