PRODUCTION OF SULPHITE PULP FROM SPRUCE. 7 
METHOD OF CONDUCTING EXPERIMENTS. 
LIQUOR MAKING. 
The sulphur dioxide used in making the liquor in these experiments 
was obtained in liquid form under pressure in iron cylinders 5 feet 
5 inches in height and 11 inches in diameter, each cylinder holding 
about 200 pounds. By obtaining the sulphur dioxide in this way 
the cooking liquor can be made to any desired strength in a couple of 
hours by simply turning a valve, which is an ideal way of handling 
the gas for experimental work. 
In making the cooking liquor for the first cook the gas from one of 
these cylinders was passed to the bottom of an absorption tank, 
containing the desired amount of milk of lime, by means of a lead 
pipe which contained a number of small openings in the end. The 
procedure in making the subsequent liquors was as follows: When 
a cook was finished, the pressure in the digester was blown down to 
about 65 or 70 pounds, and the gas thus liberated was passed through 
a separator, which removed the liquor, to the bottom of the absorp- 
tion tank B (fig. 2) which contained a dilute solution of milk of lime. 
The liquor from tank B (fig. 2) was then pumped to the make-up | 
tank A (fig. 2) and, if necessary, water was added so that it contained 
at least 80 gallons. Sulphur dioxide gas was then passed into this 
tank from the cylinder and the liquor in the tank analyzed (for 
methods of analysis see p. —) every half hour. The rate at which 
the gas was being absorbed could then be calculated and the time in 
which the desired strength would be obtained could be determined 
very closely. The cylinder could also be put on a scale and the 
desired amount of gas calculated and the weight obtained by differ- 
ence. After the tank B (fig. 2) was emptied it was again filled with 
a dilute solution of milk of lime ‘+ and any gas that was not absorbed 
in the make-up tank passed through a lead pipe back into this tank. 
Very little gas would be given off, however, it being absorbed almost 
up to the full pressure of the cylinder. While the. gas is being 
absorbed in the make-up tank, milk of lime can be added as desired 
or cooking liquor can be made containing no lime at all. When the 
liquor is of the desired strength it is ready to be pumped to the 
digester to start the next cook. 
While these experiments were in progress it became impossible to 
secure a supply of liquid sulphur dioxide, and in order to continue 
it became necessary to make the gas. A description of some of the 
methods tried may be of assistance to anyone contemplating doing 
experimental work along this line. 
1 The lime used in the experiments had the following analysis: 
Si@peaaegtrreor eee rity BPS oF OxS6P IMC OR? tyes. seen ee ee ee ERC EE Eye ees atta 32. 31 
Hen OxerAlyO aos rp aia aio ccs nile = = SUSE 1. 20 CO2&H20 De ae ISS SER SR mE oe 1. 90 
(CA Ose Ra ee Osa re nGeds SRA eee See eas 64. 19 
