Fundamental experiments on cooking of red pine by the sulphate process are carried out to check the influence of various faction governing the cooking. It is confirmed that the best sulfidity is about 40-45% when the amount of chemicals (as NaOH) added to the chips, being 25-30% and F. S. Hanson's minimum effective alkali, proved to be 15-16%.
The cooking temperature simply accelerates the cooking speed. Thus, the rise of 10°C in temperature accelerates the speed by 25 times, but it has no influence upon the analytical value of pulp of the same yield.
The destruction of fiber seems not to be taken place up to the cooking stage of 5 and 4%lignin content, when the amount of chemicals is 25 and 30% respectively. If the cooking is carried on beyond this stage, the destruction of fiber is observed, resulting in rapid lowering of polymerization and viscosity and decrease of hydro-carbon. In case the amount of chemicals is 20%, the lignin content will not go down less than 7% and further cooking will only result in the injury of fibrous matter.
In short, 20 %, chemicals is the least amount for the sulphate cooking of red pine, and 22-23 % will be the proper amount in actual practice, but. it is quite useless to, raise this amount as high as 30 %.
The greater the amount of cooking liquor, the better the analytical value, but practically it is not worth taking into consideration.
The relation between the amount of liquor, the consistency of liquor and the amount of chemicals is shown by a graph and their influences over reaction speed are made clear.
The influences of Na2CO3, Na2SO4, Na2SO3, Na2S2O3 and the reuse of black liquor are studied, too.
