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ical difificulties and it remained for 

 George Fry and his collaborator, Carl 

 Daniel Eknian, a Swede, to perfect and 

 operate the process. The first sulphite 

 woodpulp of any commercial value was 

 made at the Bergvik mill in Sweden in 

 1874. In the United States the Ekman 

 process was operated in the mills of the 

 Richmond Paper Company at Provi- 

 dence, R. I., in 1885. The liquor origi- 

 nally used for digesting the woodpulp 

 consisted of an acid solution of mag- 

 nesium sulphite, the magnesia being ob- 

 tained by burning magnesite imported 

 from Greece. 



Mechanical difificulties surrounded the 

 operation from the outset, though the 

 quality of pulp produced was excellent. 

 The digesters in which the wood was 

 cooked were lined with lead, and the 

 heat developed in the acid liquor proved 

 to be exceedingly disturbing, as while 

 the lead expanded during the applica- 

 tion of heat, it did not contract again 

 when cold. The cost of repairs to di- 

 gesters necessitated by the behavior of 

 the lead lining was heavy, amounting to 

 $10 a ton on the total production. The 

 difficulty was overcome by the invention 

 of a digester lining composed of heavy 

 cement backing faced with brick, the lat- 

 ter being pointed with litharge and 

 glycerin. The invention of a digester 

 lining vi^as one of the important early 

 contributions of the chemical engineer 

 to the development of the industry. 



The magnesium bisulphite process, 

 originated by Ekman in Sweden, and de- 

 veloped by Charles S. Wheelwright and 

 his brothers in this country at the Rich- 

 mond mill in Providence, R. I., has been 

 modified in several particulars, the chem- 

 ical solvent now employed being bi- 



sulphite of lime, as already mentioned. 

 Several different kinds of pulp are ob- 

 tained according to the system of cook- 

 ing employed, the concentration of cook- 

 ing liquor, time of digestion and the 

 pressure employed. 



The sulphite process of cooking wood 

 is not applicable to all woods. It works 

 best with spruce and coniferous woods 

 generally. The Mitscherlich system of 

 sulphite cooking yields a product by pro- 

 longed digestion in a weak solution of 

 sulphurous acid under low pressure. 

 The resulting pulp is remarkable for 

 strength of fiber. The wood is steamed 

 for a few hours before being boiled 

 with the acid liquor. The Ritter-Kellner 

 quick-cook process is an improvement on 

 the other processes, and is the one gener- 

 ally used in this country. 



It will be seen that the process of di- 

 gesting the wood with a solution of lime 

 or magnesia in sulphurous acid sug- 

 gests an operation in pharmacy, but the 

 preparation of the wood, its limited com- 

 minution, and the final disposition of the 

 exhausted digestion liquor emphasize 

 the dissimilitude of the respective 

 maceration systems of tne pulp maker 

 and the pharmacist. By the solvent ac- 

 tion of the chemical solution upon the 

 non-fibrous constituents of the wood, the 

 cell walls or cellulose are set free from 

 their enveloping bodies and recovered to 

 the extent of nearly 50 per cent, of the 

 total weight of the wood. The mate- 

 rial which is extracted, consisting of all 

 the soluble constituents of the wood — 

 the gums, resins, tannins and active 

 plant principles in which the cell walls 

 or fibers are buried — represent to the 

 pulp maker so much ofifal or waste, 

 which is usually run oflf into rivers and 



