Table 97

Tests

After the separation of the acetone and n-butyl alcohol at the factory the purity of these compounds is tested as follows :The analysis of acetone includes the determination of specific gravity which in acetone for use in cordite manufacture should not exceed 0.800 at 15o / 15°.

1 Trans, Chem, Soc, 1917, 115, 1491.

It should be free from colour, and miscible with water in all proportions, showing no turbidity.

On evaporation there should be no more than a slight trace of residue.

The absence of certain compounds is shown by the permanganate test. In this test 1 c.c. of a 0.1 per cent solution of potassium permanganate is added to 100 c.c. of acetone. The solution is kept at 15° C, and is shielded from direct light. The characteristic pink colour produced by the permanganate should not disappear in less than 30 minutes. With the acetone produced as described above it is quite usual for this pink colour to remain for several hours.

Alkalinity is tested for by titrating a diluted solution (50 per cent of water) with N/20 sulphuric acid, paranitrophenol solution being used as indicator.

Acidity due to the presence of slight traces of carbon dioxide and volatile acids (e.g. acetic acid) should not exceed 0.002 per cent calculated as carbon dioxide. The acetone must be free from fixed acids. Total acidity is estimated as follows. A mixture of equal parts of acetone and neutral water is titrated with N/20 potassium hydroxide solution, phenolphthalein being used as indicator. Fixed acids are tested for in the following manner. 50 c.c. acetone are mixed with 50 c.c. neutral water to which a few drops of phenolphthalein solution have been added, and which has been made just pink by the addition of a drop of N/20 potassium hydroxide solution. The acetone is evaporated off on the water bath. The pink colour should return or remain, showing the absence of fixed acids.

Only traces of aldehydic and other substances that will reduce ammoniacal silver solutions are permitted. These impurities are tested for with a solution made by dissolving 3 grams of silver nitrate, 3 grams of caustic soda, and 20 grams of aqueous ammonia (sp. gr. 0.9) in water and making up to 100 c.c. 2 c.c. of this solution are added to 10 c.c. of acetone diluted with an equal quantity of distilled water and the mixture allowed to stand in the dark for fifteen minutes. The liquid is then decanted from the precipitated silver, and tested to ascertain whether excess of silver is still present. If there is excess of silver present then it is assumed that the amount of "aldehyde " in the acetone is less than one part in a thousand.

n-Butyl Alcohol n-Butyl alcohol is a comparatively new industrial substance, and its commercial applications have not yet been developed. Its most important use will probably be as a solvent.1 Even when it was only known as a laboratory product its use as a solvent for cellulose esters was suggested by R. Schupphaus (U.S. Pat. 410204/1889. Cf. also Mosenthal, J.S.C.I., 1904). Derivatives of n-butyl alcohol such as n-butyl acetate should have wide industrial application.

Another use of n-butyl alcohol will be in its application in synthetic organic chemistry. From n-butyl alcohol such compounds as n-amyl alcohol, n-valeric acid, and methyl ethyl ketone can be prepared in good yield. This latter substance has been prepared industrially from n-butyl alcohol.1 The n-butyl anilines, n butyl toluidines, and amino-butyl benzenes have also been investigated.2

1 Cf. U.S. Pat. 1321611 and 1341745.

The closing of many alcohol distilleries in Russia and the United States since the passing of prohibition will reduce the available supply of fusel oil, with the result that an increased demand for some alternative substance such as n-butyl alcohol will probably arise.

The n-butyl alcohol run off from the separators in both the continuous stills described consists of a saturated solution of water in n-butyl alcohol, with traces of ethyl alcohol. A considerable amount of water can be removed from this mixture by salting out with sodium chloride. The n-butyl alcohol supplied for industrial purposes has generally been prepared in this manner and contains not more than 10 per cent of water. The n-butyl alcohol is usually sold as 90 per cent butyl alcohol by weight. Salt remaining from the dehydration process is generally present as an impurity. In addition a small quantity of acetone - 0.5 to 1 per cent - and some lower alcohols are often present in the commercial n-butyl alcohol.

To obtain pure n-butyl alcohol the crude liquid from the salting plant must be redistilled.

A process for the removal of the last traces of water by distilling in presence of benzene has been referred to in an earlier section of this book.

n-Butyl alcohol has a density of 0.80974 at 20°/4° and boils at 117.6/763 mm.

The boiling point of the azeotropic mixture of n-butyl alcohol and water is 92n25° - the mixture being heterogeneous.

The percentage by weight of water in the azeotropic mixture is approximately 37 per cent.

n-Butyl alcohol is a colourless liquid completely soluble in hydrochloric acid (20 per cent). The purity of the alcohol can be determined by means of the temperature of critical solution of a ternary mixture of the alcohol with hydrochloric acid ; the upper critical solution temperature is 43.55° and the lower 9.6°. The c.s.t. is very sensitive to the presence of impurities.5