Sulphuric acid, preparation

C2He04S, Et0)(H0)S02. Oily acidic liquid. Soluble in water and slowly hydrolysed by it to ethanol and sulphuric acid. Prepared by passing ethene into concentrated sulphuric acid or by heating ethanol and sulphuric acid. Gives ethene when heated alone, and diethyl sulphate when heated with ethanol at 140 C. Forms crystalline metallic salts which are soluble in water. 

The aniline and the monomethylaniline can be obtained from their respective sulphonyl derivatives by hydrolysis with 70% sulphuric acid (preparation, p. 109), the mixture of the sulphonyl compound and the acid being gently boiled under reflux to illustrate the separation of the three amines, however, this is not necessary. 

This product is sufficiently pure for the preparation of phenylacetic acid and its ethyl ester, but it contains some benzyl tso-cyanide and usually develops an appreciable colour on standing. The following procedure removes the iso-cyanide and gives a stable water-white compound. Shake the once-distilled benzyl cyanide vigorously for 5 minutes with an equal volume of warm (60°) 60 per cent, sulphuric acid (prepared by adding 55 ml. of concentrated sulphuric acid to 100 ml. of water). Separate the benzyl cyanide, wash it with an equal volume of sa+urated sodium bicarbonate solution and then with an equal volume of half-saturated sodium chloride solution- Dry with anhydrous magnesium sulphate and distil under reduced pressure. The loss in washing is very small (compare n-Butyl Cyanide, Section 111,113, in which concentrated hydrochloric acid is employed). 

Physical Properties of Perdisulphuric Acid.—Pure perdi-sulphuric acid, prepared as described, is a hygroscopic crystalline solid which melts near 65° C. with partial decomposition. It gradually decomposes at the ordinary temperature with liberation of oxygen. 

Dinitro-2-phenylbenzoselenazole, C13H7(N02)2NSe.—A solution of 2-phenylbenzoselenazole (25 grams) in 150 c.c. of concentrated sulphuric acid prepared at 5° to 10° C. is cooled below 0° C. and a well-cooled mixture of 9-5 grams of concentrated nitric acid and 15 grams of concentrated sulphuric acid added very slowly with mechanical stirring. After stirring for two hours below 0° C., a similar quantity of 66 mixed... 

Substituted aromatic carboxylic acid amides of the type ArCONHR and Ar-CONR2 are only slowly attacked by aqueous alkali and are characterised by hydrolysis under acidic conditions 70 per cent sulphuric acid (prepared by carefully adding 4 parts of acid to 3 parts of water) is the preferred reagent. Use the general procedure which has been outlined on p. 1229 characterise the acidic and basic components. 

To 5 c.c. of the solution of sulphurous acid prepared in Experiment 60 add 5 c.c. of chlorine water, shake the solution and then test for a sulphate. (4) What was the result of the test (5) Write the equation for the reaction. (6) What was oxidized (7) What was the oxidizing agent (8) As what kind of an agent did the sulphurous acid act ... 

Sugar liquors, purification of, 50. Sulphides, preparation of, 42. Sulphuric acid, preparation of, 28. 

N arsenious acid reagent. Dissolve 3 71 g of arsenious oxide in 7 ml of ION sodium hydroxide, add 300 ml of redistilled water and neutralise to methyl orange with ION sulphuric acid (prepared from 18N acid, below). Add 21 ml of concentrated sulphuric acid and dilute to 500 ml with redistilled water. 

Boil the sample with water, cool and dilute with water to give a solution containing 10 to 200 / g of starch in 2 ml. If the solution contains suspended material, filter through dry paper. Pipette 2 ml of the clear solution into a test-tube and at the same time pipette 2 ml of water into a second test-tube for the blank and prepare one or more 2-ml standards using suitable weights of pure starch (100 /wg is suitable) in 2 ml dissolved in water by boiling. To each test-tube add, rapidly from a pipette or burette, 4 ml of a 01 per cent solution of anthrone in concentrated sulphuric acid (prepared at least four hours and not more than nine days before use) it is important that the reagent be added in exactly the same way to all the tubes. Mix the contents of each tube, allow to cool in air for ten to fifteen minutes and then cool completely in a bath of cold water. 

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