ree times the amount of water lost
by evaporation. On the other hand, a damp flour dried too quickly and at
too great a heat is liable to be made more instead of less susceptible
to diastasic changes.

_Alum._--Strictly speaking, when employed with weak and unstable
flours alum is a remedial agent. The popular idea that it acts as a
kind of bleacher of flour, having the faculty of converting flour that
is dark-coloured through containing a sensible proportion of branny
particles and woody fibre, into white-coloured loaves, is erroneous.
Its action as a producer of white bread is indirect, not direct,
though it is none the less effective. It seems to act as a brace to or
steadier of unstable gluten. If from the same wheat a certain
proportion of gluten be extracted and divided into two parts, of which
one is placed in a glass of water containing a strong solution of
alum, and the other in a glass of plain water, the gluten in the
latter case will become spent days and perhaps weeks before the sample
in the alumed water is disintegrated. The place of alum in the process
of fermentation is well marked. By holding together unstable gluten,
it checks the diastasic action, and the proportion of starch converted
into glucose (grape sugar) is reduced, with the result that a whiter
and more porous loaf is produced. It is generally admitted that by the
use of alum more or less eatable bread may be baked from flour which
otherwise could hardly be made into bread at all. Strictly, therefore,
this substance is not an adulterant, inasmuch as it is not a
substitute in any sense for flour. But it is admittedly unwholesome,
and therefore its legal interdiction for alimentary purposes is quite
justifiable. Another aspect of the use of alum is that it is employed
for the purpose of enabling bakers to use poor flour.

A fairly satisfactory test for alum in bread (or flour) is afforded by
an alkaline solution of logwood and a saturated solution of ammonium
carbonate. The presence of alum is shown by a lavender or full blue
colour. The depth of the tint is said to be a rough guide to the
quantity of alum present. According to Jago this test is so sensitive
that it has resulted in the detection of 7 grains of alum in a 4-lb
loaf.

Besides alum, small quantities of copper sulphate have been used for
checking diastasis and retarding fermentation. This substance has the
same