substance is weighed after cooling, and is pyrophosphate of magnesia,
from which the magnesia or carbonate of magnesia is calculated
stoichiometrically. All the ascertained sums must be multiplied by 2,
if they are to correspond to the analyzed and weighed quantity of ash.

The second half of the filtrate is used for determining the small
quantity of sulphate of lime still contained in the hydrochlorate
solution. By adding chloride of barium solution the sulphuric acid is
bound to the barytes and sulphate of baryta separates as white
precipitate. This is separated by filtering, washed, dried and weighed
in the customary manner. From the weight of the sulphate of baryta is
then computed the weight of sulphate of lime, which has passed over
into solution. The ascertained sum is also to be multiplied with 2.

The manufacture of roll tar paper from the roll paper was at first
found to be difficult, as it was impossible to submerge a surface
larger than from ten to fifteen square yards, rolled up, in the tar,
because more would have required too large a pan. Besides this, the
paper tears easily, when it is in the hot tar. All kinds of
experiments were tried, in order to impregnate the surface of the
paper without employing too large a pan.

The following method was tried at first: The roll paper was cut into
lengths of ten yards, which were rolled up loosely, so that a certain
space was left between the different coils. These loose rolls, of
course, occupied much space and could be put into the tar only in a
standing position, because in a horizontal one the several coils would
have pressed together again. The loose roll was therefore slipped over
a vertical iron rod fastened into a circular perforated wooden foot.
The upper end of this iron rod ended in a ring, in which the hook of a