26$ Dr, Colquhoun's Essay [Oct. 



or with zinc filiugs, and th^n kneading it into a paste by mean^ 

 of water acidulated with sulphuric acid, he always met with 

 complete failure and disappointment.* 



As it was a question certainly of considerable interest to 

 ascertain how the truth lay between the conflicting statements 

 which have just been detailed, and also of much practical 

 importiince, to prove the eflect of carbonic acid gas introduced 

 into bread without the aid of fermentation, it seemed a matter 

 well worthy of attention to subject the point anew to the test of 

 experiment. This inquiry implied, of course, a two-fold inves- 

 tigation. It was desirable, in the first place, to determine the 

 practicability of obtaining a well-raised loaf, from dough formed 

 by mixing flour with a saturated aqueous solution of carbonic 

 acid gas. To resolve this point conclusively, it was necessary 

 to try the effect of baking such dough, both when perfectly 

 recent, and also after having been kept for some time, in order 

 to ascertain whether the saturated solution might in this latter 

 case be capable of exciting the saccharine fermentation, without 

 the assistance of yeast. And, in the second place, it was 

 important to decide whether the effects of the slow yeast-fer- 

 mentation might be imitated, with reference to the lightness and 

 porosity of the bread, by blending the dough intimately with an 

 alkaline carbonate, and subsequently causing a sudden disen- 

 gagement of carbonic acid gas within its substance by the 

 addition of an acid. The results that were obtained seem to be 

 conclusive on both branches of the research. 



Four ounces of flour were made into dough with four cubic 

 inches of a saturated aqueous solution of carbonic acid gas at 

 the temperature of 51°. A second portion of dough was pre- 

 pared by mixing two ounces of flour into a paste with two cubic 

 inches of water, at the temperature of 80°, and immediately 

 afterwards kneading it with two ounces additional of flour, and 

 two cubic inches of carbonic acid gas. For the purpose of com- 

 parison, a third portion of dough was prepared, with four ounces 

 of flour, and four cubic inches of a mixture of yeast and warm 

 water at a temperature of about 70°. To each of these three 

 masses of dough there were besides allowed 30 grains of com- 

 mon salt, added, according to the usual practice of the baker, 

 with a view to the flavour of the bread. Immediately after their 

 preparation, a portion (about one-fourth) was detached from 

 each, and baked in the oven. The products of all the three 

 |;rials were identically the same ; being a compact, unvesicular 

 bread, differing in no respect from what would have been 

 obtained by treating in a similar manner a simple mixture of 

 flour and water. 



In order to promote the fermentative process, the remainders 



* Journal de Phannacic, vol. iii. p. 216. 



