682 



EEPORT — 1892. 



These niimters were obtained immediately after the thermometer became 

 steady. In the case of the dichloriodides the thermometer rose more or less rapidly 

 as the ebullition was prolonged, and the molecular weight in consequence de- 

 creased, sinking to almost half the value indicated by the formula RXj. That 

 decomposition takes place in the case of the dichloriodides can also be seen from the 

 change of colour in the solution, which, at first pale yellow, passes through deep 

 yellow and orange to red. 



These results tend to confirm our opinion that it is impossible to draw any 

 sharp distinction between ' atomic compounds ' of great stability under conditions 

 of very varied character and ' molecular compounds,' which are unstable under 

 the same conditions. For the perfectly stable methylpyridium dibromiodide and 

 the unstable trimethylsulphine trichloride, which can only exist in an atmosphere 

 of dry chlorine, are perfectly analogous compounds, and are merely the end terms 

 of a series, the intermediate terms of which have intermediate degrees of stability. 



8. The Production of Acetic Acid from the Garhohydrates. 

 By J. F. V. Isaac, B.A. 



The purpose of this i-esearch is to give a quantitative account of the decompo- 

 sition of the carbohydrates by ' fusion ' with alkaline hydrates, regulating the 

 conditions of the decomposition so as to give the maximum production of acetic 

 acid. To determine this maximum and the conditions under which it is attained, 

 the several factors have been varied, and the eflects of the variations ascertained. 

 Thus temperature, time, nature of alkaline hydrate (NaOH, KOII, <&c.), and pro- 

 portions of the alkali to carbohydrate have been investigated ; and further various 

 carbohydrates of typical constitutions have been studied, chiefl}' cane sugar, cellu- 

 lose (cotton, fl^ax, and other forms), hydracellulose (product of action of concen- 

 trated hydrochloric acid on cotton cellulose), jute, and pine wood. The following 

 are the more important results : — 



Temperature. — The formation of acetic acid is observable at 100-110° C. ; 

 it becomes considerable at 150° C, and reaches a maximum at 250-350° 0. 



7Y?«e. — The duration of the heating is, as might be expected, of considerable 

 influence at the lower temperatures ; at higher temperatures the decompositions 

 are rapidly completed. 



As regards the alkali and the proportion of alkali to carbohydrate, the maxi- 

 mum yields are obtained with potassium hydrate, and in the proportion of three 

 parts to one of carbohydrate. 



The various carbohydrates above named appear to yield approximately the 

 same maximum of acetic acid, viz., from 30-40 per cent, of their weight under tlie 

 most favourable conditions. The addition of weak oxidising agents, e.ff., ferric 

 hydrate and potassium ferricyanide, tends to increase the yield of acetic acid, 

 more especially at the lower temperatures. 



The other products of the decomposition are oxalic and carbonic acids, together 

 with gaseous compounds continuously evolved. In addition to hydrogen, which 

 is the chief constituent, a small quantity of a gaseous carbon compound is 

 formed, presumably CH^ or CO. On passing the gases evolved from the decompo- 

 sition of sugar with potassium hydrate over red-hot copper oxide in a combustion 

 tube the atomic ratio of the H to C determined was found to be in two experi- 

 ments '29 : 1 and 20 : 1 respectively. The hydrogen evolved was found to be from 

 40-50 per cent, of that contained in the original substance. 



