CHEMICAL SCIENCE. 27/5 



carbonate of soda, and 21 ounces of tartaric acid, severally dissolved in 

 lukewarm water, together with H pounds of common yeast. The mass will 

 now require hot or cold water to bring it to 27 R., when it is left twelve 

 hours to ferment. After this it is pressed through a hair sieve, and in eight 

 or ten hours the yeast forms on the bottom of the cask. This yeast is 

 taken and put into double bags, which are submitted to pressure to free it 

 from moisture. 



NEW PROCESS OF BREAD-MAKING. 



The following is an account of a new process of bread-making recently 

 put in practical operation by Dr. Dauglish, of Carlisle, Scotland : 



According to the ordinary process, fermentation is produced by the action 

 of the yeast upon the particles of starch in the flour, thus liberating minute 

 bubbles of carbonic acid gas, which permeate the entire mass of the dough, 

 and make it "rise." The chemical change, however, which here takes 

 place, is such that it has been estimated by M. Dumas, that in France Ilk 

 per cent, and in England 8 to 12 per cent, is wasted by the decomposition 

 which takes place in the process of fermentation. In the new process, 

 patented by Dr. Daug-lish, no yeast or baking powder is used, the rising of 

 the dough being effected by water impregnated with carbonic acid gas. 

 The idea of making bread with aerated water is not a new one ; a patent 

 was taken out for such a process some years ago, but it was then found that 

 when the flour was mixed with the impregnated water the gas escaped 

 before the bread had time to rise. The novelty of Dr. Dauglish's patent 

 consists in preventing the escape of the gas from the water, by subjecting 

 the materials to an outward pressure of carbonic acid gas while the flour is 

 being mixed with carbonated water. The carbonic acid gas is generated in 

 such apparatus as is usually employed by soda-water manufacturers; the 

 gas is pumped into a large reservoir, from which it is forced, as it is required, 

 into a vessel containing water the absorbing power of water for car- 

 bonic acid being very great. The kneading machine is a strong iron retort, 

 fitted with air-tight lids, and provided with revolving prongs in the inside 

 for mixing the dough. In the machine now in operation, this retort is 

 capable of containing forty stones of flour. Into this are put twenty stones 

 of flour, with the requisite amount of salt. A stream of carbonic acid gas 

 is forced into the retort, and a sufficient quantity of carbonated water is 

 admitted and well mixed with the flour and salt; the gas with which the 

 water is impregnated being prevented from escape by the pressure of the 

 ambient carbonic acid gas. As soon as the flour and water are mixed, a 

 pipe is opened, and the loose gas is let out. The consequence of the pressure 

 being taken away from the surface of the paste is that the gas which was 

 held in solution by the water operates in precisely the same manner as the 

 gas in a bottle of soda-water when the cork is removed, the dough rises and 

 fills the retort, occupying twice as much space as before. The bread is then 

 ready for being worked into loaves the only operation that will necessi- 

 tate handling. The rising can be regulated by the pressure of gas: so that, 

 did the strength of the machinery permit, the bread might be made of 

 almost any lightness. The pressure of the gas, and the quantity of water 

 admitted, are regulated by gauges. 



