2 BULLETIN 620, XT. S. DEPARTMENT OF AGRICULTURE. 



base is present. Lime is the base in most common use. For a 

 long time it was not known how much of this was necessary to make 

 good pulp, most mills simply taking the acid that their systems 

 gave them. Many are still following that practice. Most mills 

 have a good idea of how the different factors affect their cooking, 

 but there is no published report on the subject. It was to furnish 

 detailed information on just how much each of the various factors 

 influences the cooking and to supply a basis for future experimental 

 work that this investigation was undertaken. 



THE SULPHITE PROCESS. 



The inventor of the sulphite process, Benjamin C. Tilghman, of 

 Philadelphia, took out a patent in the year 1867, in which he describes 

 a method of boiling under pressure wood or other vegetable material 

 in a solution containing sulphurous acid, with or without the addition 

 of sulphites, until a fibrous product is obtained suitable for the manu- 

 facture of paper. The foundation of the sulphite pulp industry 

 rests upon these patents; yet Tilghman had to abandon his process 

 because his financial backers withdrew their support upon finding out 

 that sulphurous acid corrodes iron and that the inventor was having 

 difficulty in obtaining a suitable lining for his digester when he tried 

 to work his process on a large scale. 



For some time this difficulty hindered the development of the 

 process. In 1886 cement and special brick linings were introduced 

 in some mills and gave such good satisfaction from the start that it 

 was not long before they were universally adopted. The solution 

 of this problem insured the com m ercial success of the sulphite in- 

 dustry, and from this time on it has had a rapid growth, until now 

 it is the most important pulp making process in the United States, 

 as is shown by the figures in Table 1 taken from the census reports. 



Table 1. — Quantity of wood pulp produced in the United States. 



Process. 



1890 



1899 



1909 



Value 

 (1909). 



1916 



Value 

 (1916). 





Tons. 



59, 686 



87, 853 



290, 158 



Tons. 

 417,646 

 172, 142 

 568, 284 



Tons. 

 1, 027, 012 



287, 945 

 1,201,832 



$44,600,000 

 12, 770, 000 

 25, 200, 000 



Tons. 

 1,306,217 



183,106 

 1,505,547 



860,702,459 

 8,251,219 







32,547,704 







KINDS OF WOOD USED. 



In the early days spruce was almost the only wood used in making 

 sulphite pulp, but it was not long before hemlock and balsam began 

 to be used extensively. At the present time some mills are cooking 

 tamarack and poplar, and on the west coast white, red, amabilis, and 

 grand fir, sitka and Engelmann spruce, western hemlock, and other 

 woods are finding favor. No doubt it will not be long before 



