Weight of paper
expressed in
millimetres.
:
100
::
5·5
Weight of ash
expressed in
millimetres.
:
11·224
Percentage
of ash
in paper.
In order to ascertain the percentage of mineral matter actually added to a paper it is necessary to deduct from the amount of ash obtained a certain quantity due to the mineral matter in the fibre of which the paper is composed. This amount varies with each particular fibre, and with the method by which it has been prepared. The following table gives the percentage of ash yielded by the various pulps in a perfectly bleached state. In all cases the fibres were previously treated with a dilute solution of hydrochloric acid, in order to remove any carbonate of lime or other bodies which might have been introduced in the boiling and bleaching processes: the percentages are calculated on the dry substances:—