274 Use of Sulphate of Copper, fyc. in Bread. 



Suh- Carbonate of Magnesia. 



Il has been slate'd by Edmund Davy, ihat from 20 to 40 grains of 

 sub-carbonate of magnesia, intimately mixed with one pound of bad 

 flour, will materially improve the quality of the bread. It is proba- 

 ble that the carbonate is converted by the fermentation into an ace- 

 tate, and although the quantity of magnesia above mentioned may do 

 no, harm, it may not be amiss to show how it may be detected. Por- 

 phyrise the ashes of 200 grains, (or a larger quantity in any case if 

 desirable,) dilute with acetic acid, and evaporate to dryness to expel 

 any excess of acid. Treat the dry mass with alcohol and filter j 

 evaporate again to dryness, and redissolve in a little water. 



To this solution add a slight excess of bi-carbonate of potash and ' 

 filter. By boiling this filtered liquid, the magnesia, if any exist, will 

 separate in a white jelly. This process might be much simplified, if 

 there did not exist in flour, phosphate of magnesia, the solution of 

 which must be avoided. 



AUcaline Suh-carhorMies, 



Many authors assert that sub-carbonate of ammonia conlributes 

 powerfully to promote the rising of bread, and to increase its white- 

 ness. The volatility of this salt may possibly aid mechanically the 

 extension of the dough, but since it is probable that the acetic acid 

 developed by the fermentation would combine with the ammonia, it 

 is doubtful whether much benefit would be derived from the use of 

 this salt, unless employed in very large doses. 



The existence of this or other alkalies can be detected by the 

 methods which depend on their soldbility, and other peculiar pro- 

 perties. 



• Other Subsianees. 



Chalk, pipe cby and plaster have also been employed in the adul- 

 teration of bread. The design in these cases is to increase the 

 weight of the bread and perhaps its whiteness. Their piesence may 

 be shewn, both by the increased weight which they give to the ashes, 

 and by the tests usually employed to distinguish their component" 

 parts. 



