PRODUCTION OF SULPHITE PULP FEOM SPEUCE. 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 x 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 



Si0 2 0. 56 



Fe 2 03&Al 2 03 1. 20 



CaO 64. 19 



MgO 32. 31 



CO2&H2O 1.90 



