tity, to a certain extent were found to improve the bread made
from new flour; but no substance was so efficacious in this respect as
carbonate of magnesia.

"The greater number of his experiments were performed on the worst new
_seconds_ flour Mr. Davy could procure. He also made some trials on
_seconds_ and _firsts_ of different quality. In some cases the results
were more striking and satisfactory than in others; but in every
instance the improvement of the bread, by carbonate of magnesia, was
obvious.

"Mr. Davy observes, that a pound of carbonate of magnesia would be
sufficient to mix with two hundred and fifty-six pounds of new flour, or
at the rate of thirty grains to the pound. And supposing a pound of
carbonate of magnesia to cost half-a-crown, the additional expense would
be only half a farthing in the pound of flour.

"Mr. Davy conceives that not the slightest danger can be apprehended
from the use of such an innocent substance, as the carbonate of
magnesia, in such small proportion as is necessary to improve bread from
new flour."

METHOD OF DETECTING THE PRESENCE OF ALUM IN BREAD.

Pour upon two ounces of the suspected bread, half a pint of boiling
distilled water; boil the mixture for a few minutes, and filter it
through unsized paper. Evaporate the fluid, to about one fourth of its
original bulk, and let gradually fall into the clear fluid a solution of
muriate of barytes. If a _copious_ white precipitate ensues, which does
not disappear by the addition of _pure_ nitric acid, the presence of
alum may be suspected. Bread, made without alum, produces, when assayed
in this manner, merely a very slight precipitate, which originates from
a minute portion of sulphate of magnesia contained in all common salt of
commerce; and bread made with salt freed from sulphate of magnesia,
produces an infusion with water, which does not become disturbed by the
barytic test.

Other means of detecting all the constituent parts of alum, namely, the
alumine, sulphuric acid, and potash, so as to render the presence of the
alum unequivocal, will readily suggest itself to those who are familiar
with analytical chemistry; namely: one of the readiest means is, to
decompose the vegetable matter of the bread, by the action of chlorate
of potash, in a platina crucible, at a red heat, and then to assay the
residuary mass--by means of muriate of barytes, for sulphuric acid; by
ammonia, for alumine; and by muriate of platina, for