Volatility in steam

Although Si(OH) is nonvolatile at ordinary temperature and polymerizes quickly when heated, nevertheless at elevated temperature and pressure in-water its solubility is greatly increased and it can exist in equilibrium as the vapor phase in the steam, as shown by Kennedy (25). This is of importance in very high pressure boilers in power plants where deposits build up on turbine blades unless all silica is removed from the feedwater. Brady (26) supposes the volatile species is Si(OH)4 o., (HO)3SiOSi(OH)3. Astrand (27) found that volatility increased with decreasing alkalinity in experiments conducted up to 350°C and 300 atm. This, of course, suggests that Si(OH)4 is more volatile than the silicate ion. Wendlandt and Glemser (28) reviewed evidence from earlier workers and calculated the equilibrium constants involved whence the species in the vapor were related to the density of the water vapor  

Similarly, Martynova, Fursenko, and Popov (29) found that in a solution saturated with soluble silica at 263-364 C about a third of the silica in the vapor was present as drsilicic acid, whereas in the range 151-223 C it was all monomeric. 

Heitmann (30) concluded that deposition in turbines was minimal if the silica concentration was less than 0.01 ppm, iron concentration less than 0.005 ppm, and the conductivity less than 0.1 micromho cm . According to Heitmann s measurements (31), the silica concentration in the vapor phase ranges from 0.1 mg kg r 400 C to 5 mg kg- at 600 C at a pressure of 0.3 kg cm , but increases to mor,. than 100 mg kg under an applied pressure of 300 kg cm.  

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Colourless liquid with a strong peppermintlike odour b.p. 155" C. Manufactured by passing cyclohexanol vapour over a heated copper catalyst. Volatile in steam. Oxidized to adipic acid. Used in the manufacture of caprolactam. Nylon, adipic acid, nitrocellulose lacquers, celluloid, artificial leather and printing inks. 

The lower members of the series are liquids soluble in water and volatile in steam. As the number of carbon atoms in the molecule increases, the m.p. and b.p. rise and the acids become less soluble in water and less volatile. The higher fatty acids are solids, insoluble in water and soluble in organic solvents. 

For small quantities of compounds which are readily volatile in steam, it will often suffice to add water to the crude material in the reaction flask e.g,., Fig. 36) and to heat directly with a small flame. 

Then detach and reverse the condenser, and reconnect it to the flask through a knee-tube for direct distillation, as shown in Fig. 60, p. 101, or Fig. 23(0), p. 45. Distil the mixture, by direct heating over a gauze, until about 8 ml. of distillate have been collected. Acetic acid is volatile in steam and an aqueous solution of the acid, containing, however, some acetaldehyde, is thus obtained. With a very small portion of this solution, perform the tests for acetic acid given on p. 347. 

Volatility in steam. Add about 0 1 g. of benzoquinone to 3 ml. of water in a test tube and boil gently. The benzoquinone dissolves to give a yellow solution, which rapidly darkens in colour. Note the irritating and characteristic odour of benzoquinone which has volatilised in the steam. Also given by />-toluquinone and 1,4 naphthoquinone but not by the other quinones mentioned above. 

Physical Properties. Both solids, freely soluble in hot water, sparingly in cold water. o-Nitrophcnol, bright yellow, volatile in steam, odour resembling both that of phenol and of nitrobenzene />-m trophenol, colourless when pure, non-volatile in steam, odourless. 

Volatility in steam is readily observed by boiling a small quantity of the substance with water in a test-tube, and noting the appearance of drops of condensed yellow oil on the upper and cooler portions of the tube. 

It is frequently necessary to concentrate a filtrate in order to obtain a further crop of crystals, or it may be necessary to concentrate a solution to a smaller volume. If the solvent is water and the substance is not volatile in steam, simple evaporation on a large dish on a steam or water... 

Extraction of steam distillates by solvents. The apparatus, depicted in Fig. 11,58, 7, may be employed for the continuous extraction of substances which are volatile in steam from their aqueous solutions or suspensions. Solvents of the ether type (i.e., lighter than water) or of the carbon tetrachloride type (i.e., heavier than water) may be used. A reflux condenser is inserted in the Bl9 socket, whilst flasks of suitable capacity are fltted into the lower B24 cone and the upper. B19 cone respectively. For extraction with ether, the flask attached to the upper. B19 cone contains the ether whilst the aqueous solution is placed in the flask fltted to the lower B2i cone the positions of the flasks are reversed... 

The ester and catalj st are usually employed in equimoleciilar amounts. With R =CjHs (phenyl propionate), the products are o- and p-propiophenol with R = CH3 (phenyl acetate), o- and p-hydroxyacetophenone are formed. The nature of the product is influenced by the structure of the ester, by the temperature, the solvent and the amount of aluminium chloride used generally, low reaction temperatures favour the formation of p-hydroxy ketones. It is usually possible to separate the two hydroxy ketones by fractional distillation under diminished pressure through an efficient fractionating column or by steam distillation the ortho compounds, being chelated, are more volatile in steam It may be mentioned that Clemmensen reduction (compare Section IV,6) of the hj droxy ketones affords an excellent route to the substituted phenols. 

To the cold acid chloride add 175 ml. of pure carbon disulphide, cool in ice, add 30 g, of powdered anhydrous aluminium chloride in one lot, and immediately attach a reflux condenser. When the evolution of hydrogen chloride ceases (about 5 minutes), slowly warm the mixture to the boiling point on a water bath. Reflux for 10 minutes with frequent shaking the reaction is then complete. Cool the reaction mixture to 0°, and decompose the aluminium complex by the cautious addition, with shaking, of 100 g. of crushed ice. Then add 25 ml. of concentrated hydrochloric acid, transfer to a 2 htre round-bottomed flask and steam distil, preferably in the apparatus, depicted in Fig. II, 41, 3 since the a-tetralone is only moderately volatile in steam. The carbon disulphide passes over first, then there is a definite break in the distillation, after whieh the a-tetralone distils completely in about 2 htres of distillate. 

Hydrolysis of a sulphonamide. Mix 2 g. of the sulphonamide with 3-5 ml. of 80 per cent, sulphuric acid in a test-tube and place a thermometer in the mixture. Heat the test-tube, with frequent stirring by means of the thermometer, at 155-165° until the solid passes into solution (2-5 minutes). Allow the acid solution to cool and pour it into 25-30 ml. of water. Render the resulting solution alkaline with 20 per cent, sodium hydroxide solution in order to liberate the free amine. Two methods may be used for isolating the base. If the amine is volatile in steam, distil the alkaline solution and collect about 20 ml. of distillate extract the amine with ether, dry the ethereal solution with anhydrous potassium carbonate and distil off the solvent. If the amine is not appreciably steam-volatile, extract it from the alkaline solution with ether. The sulphonic acid (as sodium salt) in the residual solution may be identified as detailed under 13. 

Steam distillation.—For small quantities of compounds, which are readily volatile in steam, water may be added to the contents of the reaction flask (e.g. Figs. XII, 2,4 and XII, 2, 11) and the flask heated in an air bath or with a small flame. Alternatively, if preferred, steam may be passed into the reaction flask from a separate generator this may consist of a small conical flask provided with the usual safety tube (compare Fig. II, 40, 1). 

Arecoline, CgHj 302N. This, the most important alkaloid of areca nut, is an odourless, alkaline oil, b.p. 209°, volatile in steam, miseible with most organic solvents and water, but extractable from the latter by ether in presence of dissolved salts. The salts are crystalline, but usually deliquescent the hydrobromide, B. HBr, forms slender prisms, m.p. 177-9°, from hot alcohol the aurichloride, B. HAUCI4, is an oil, but the platinichloride, B2. H2PtClg, m.p. 176°, crystallises from water in orange-red rhombs. The methiodide forms glancing prisms, m.p. 173-4°. 

Bases not Volatile in Steam. Anodmine (picrolonate, m.p. 310°), lathreine (picrolonate, m.p. 150°), and lohitam. 

Reaction.—kAd a drop of feriic chloride to the aqueous solution of the aldehyde. A deep violet colouration is producecl p-Hydi-oxybcnsaldehyde.—Colouiless needles, m. p. 115—1 16 scarcely soluble in cold water, readily in hot water, alcohol ether. Non-volatile in steam. The bisulphite of sodiutaa compound dissolves readdy in water. 

Nitro Derivatives of N-Methylaniline Nitro-N-Methylanillnes, C7H8N202, mw 152.15, N 18.41%, OB to C02 —168%. The following isomers are described in the literature N-Nitro-N-methylaniline, needles or leaflets from eth, mp 38.5—9.5°, volatile in steam without decompn (Ref 1) CA Registry No 7119-93-9... 

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