16 ACETYLENE 



commit no appreciable error. Honco a solution of the carbonate containing 200 

 grains in 100 measures will form an acetimeter of the most perfect and convenient 

 kind ; for the measures of test liquid expended in saturating any measure for instance, 

 an ounce or 1,000 grains of acid will indicate the number of grains of real acetic 

 acid in that quantity. Thus 1,000 grains of the above proof would require 50 measures 

 of the acetimetrical alkaline solution, showing that it contains 60 grains of real acetic 

 acid in 1,000, or 5 per cent. 



Although the bicarbonate of potash of the shops is not absolutely constant in com- 

 position, yet the method is no doubt accurate enough for all practical purposes. 



The acetimetrical method employed by the Excise is that recommended by Messrs. 

 J. and P. Taylor, and consists in estimating the strength of the acid by the specific 

 gravity which it acquires when saturated by hydrate of lime. Acid which contains 

 5 per cent, of real acid is equal in strength to the best malt vinegar, called by th* 

 makers No. 24, and is assumed as the standard of vinegar strength, under the deno 

 mination of ' proof vinegar.' Acid which contains 40 per cent, of real acetic acid, is 

 therefore, in the language of the Revenue, 35 per cent, over proof ; it is the strongest 

 acid on which duty is charged by the acetimeter. In the case of vinegars which have 

 not been distilled, an allowance is made for the increase of weight due to the mucilage 

 present ; hence, in the acetimetor sold by Bate, a weight, marked M, is provided, and 

 is used in trying such vinegars. As the hydrate of lime employed causes the pre- 

 cipitation of part of the mucilaginous matter in the vinegar, it serves to remove this 

 difficulty to a certain extent. (Pereira.) 



As the colour of malt vinegar or impure acetic acid sometimes obscures the exact 

 termination of the reaction, when a standard solution of carbonate of soda is used, 

 with litmus as an indicator, it is better to use the ammoniacal solution of copper 

 recommended by Kiefer. This is made by dissolving sulphate of copper in water and 

 adding solution of ammonia till the precipitate of basic salt, which forms at first, just 

 redissolves. The strength of the copper solution is then ascertained by means of a 

 standard solution of sulphuric acid. To use it a certain quantity of the vinegar to 

 bo tested is measured with a pipette- and placed in a beaker or other suitable vessel 

 and the copper solution gradually run into it from a burette. The bluish green 

 precipitate formed disappears on stirring as long as any free acid remains, but as soon 

 as it is completely neutralised a permanent turbidity is produced. A sheet of dark- 

 coloured paper placed under the beaker enables the end of the experiment to be 

 distinguished with greater facility. It is necessary that the acid should be so dilute 

 that the precipitate, which is seen on adding the first drop of copper solution, only 

 disappears on agitating the mixture ; it is then of a suitable strength. 



An excellent method, equally applicable to every description of acetic acid, has been 

 proposed by Mohr. Pure precipitated carbonate of lime or baryta is added in excess 

 to a known quantity of the acid to be tested. When the effervescence has ceased tho 

 mixture is heated, to complete the saturation of the acid and to expel the carbonic 

 acid gas. The excess of the earthy carbonate employed is then filtered off, washed 

 with hot water, and its amount ascertained by means of a standard acid and 

 an alkaline solution, as described in the article on alkalimetry, The result thus 

 obtained is subtracted from the weight of the carbonate added, and gives the 

 quantity which has been consumed in saturating the acid. 100 parts of carbonate 

 of lime dissolved, represent 102 of acetic acid, viewed as anhydrous, or 120 of the 

 hydrated acid. 



ACETONE. A volatile spirit obtained by the distillation of the acetates of tho 

 alkaline earths. It may also be prepared by the destructive distillation of citric acid, 

 or by distilling starch, sugar, or gum with quicklime. The formula of acetone is 

 C'H 8 2 (C 3 H 6 O). See PYROACETIC SPIRIT. 



ACETYXi. Some chemists (following Berzelius, who denied the existence of oxidised 

 radicals) regard acetyl as a radical, the teroxide of which constituted acetic acid. 

 The followers of Gerhardt, on the other hand, consider acetic acid to contain a radical 

 of the formula C 4 H 0- (CPH'O). The latter Is generally known as acetyl. Dr. 

 Williamson proposes to call it othyl. 



ACETYLAivnurE. C 4 H 8 N (C'H 4 !*). An oily alkaloid, produced by acting 

 with the oil of olefiant gas (Dutch liquid, or chloride of ethylene) on an alcoholic 

 solution of ammonia. 



ACETYX.EKTX. A hydrocarbon containing C 4 H 2 (C 2 H 2 ). By passing a 

 voltaic current through carbon poinls in an atmosphere of hydrogen, acetylene is 

 formed by the direct union of its elements. It may also be produced by the incom- 

 plete combustion of certain hydrocarbons, and indeed by the imperfect oxidation of 

 most organic compounds. Acetylene is a colourless gas, possessing a peculiar odour, 

 nnd burning with an intensely luminous flame. A highly characteristic reaction of 

 acetylene, by which its presence may readily be determined, is the formation of a 



