oan 
274 Use of Sulphate of Copper, Sc. in Bread. 
g 
is: Sub- Carbonate of Magnesia. 
It has been stated by Edmund Davy, that 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 couverted 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; 
evaporate again to dryness, and redissolye in a little water fo 
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. 7 a 
Alkaline Sub-carbonates. 
Many authors assert that sub-carbonate of ammonia contributes 
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, 
is doubtful whether much benefit ‘would be derived from the uit 
this salt, unless employed in very large doses. 24: 4 
_ The existence of this or other alkalies can be detected by the 
methods which depend on their solubility, and other peculiar pro 
perties. ; 
Other Substances. 
Chalk, pipe clay and plaster have also been employed in the adul- 
teration of bread. The design in these cases .is to’ increase t 
weight of the bread and perhaps its whiteness. ‘Their presence may 
be shewn, both by the increased weight which they give to the ashes; 
and by the tests. usualy employed to distinguish their component 
parts. - ; 
