324 Acid Liquid Jrom Potash ami Alcohol. 



and exactly similar to the crystals of formate of magnesia, which 

 had been obtained at a much earlier period in the comparative 

 trial. The salt of lead crystallized in prisms, and on examining 

 these, as to their solubility in water, there were evidently present 

 crystals of^a much inferior solubility to acetate of lead, although 

 apparently mixed with a more soluble salt. The conclusion which 

 appeared to follow from these observations was, that the acid 

 was a mixture of acetic and formic acids ; and the subsequent 

 examination was conducted with the view of obtaining greater 

 certainty on this point, as well as to ascertain whether the acid 

 products were formed in solutions of shorter standing than those 

 before employed. 



I accordingly examined solutions of all ages, from ten days 

 to some months ; and satisfied myself that in all cases an acid 

 product resulted, apparently increasing in quantity as the expo- 

 sure to air was prolonged. Probably the readiest way of show- 

 ing the reaction, is to place an alcoholic solution of potash at 

 the bottom of a tall glass jar, and simply to tie the mouth round 

 with filtering paper. In this way, free access of fresh air is ad- 

 mitted to tlie solution through, the pores of the paper, as the 

 absorption of oxygen goes on, and in eight oi^iten days a deep 

 coloured red solution is obtained. In this mode of operating, 

 the alcohol is of course gradually weakened by the exposure to 

 the air, and, after a certain time, the, formation of acid appears 

 not to increase. The red solution is then to be poured in- 

 to an evaporating basin, and the alcohol expelled, either by 

 heat, or, which is still better, by simple exposure to the air. 

 The residue is next to be evaporated nearly to dryness, re-dis- 

 solved in as small a quantity of water as is sufficient to take up 

 the whole, including the resinous matter, which cannot be 

 separated without at the same time separating some of the 

 acid product in combination with potash. Diluted sulphuric 

 acid is to be added at intervals to the solution contained in a 

 flask, which may be; kept cool during the. action, by plunging 

 it in water, and the whole then carefully distilled. If the pro- 

 duct of the distillation be saturated with carbonate of soda, con- 

 centrated by evaporation, again saturated with sulphuric acid, 

 and distilled in a tube retort, a more concentrated acid liquid is 

 of course obtained ; and this method may be followed in all cases 

 in which.it is wished to have a .mere concentrated liquid.; the 



