SWEDEN AND NORWAY. 491 



The wood pulp produced by the chemical process yields better results. In this 

 process, the wood is first split into chips or planed into shavings, which under 

 heavy pressure are boiled in solutions which dissolve the incrustating component 

 parts of the wood. The first chemical used on a large scale for this purpose was 

 caustic soda, but others have been used, such as sulphurous acid, sulphurous mag- 

 nesia, sulphurous lime, with some hydrochloric acid, etc. In the sulphate method, 

 sulphate of soda (glauber salt) is used together with caustic lime for the preparation 

 of caustic alkali lye. In the manufacture of soda or sulphate cellulose, the lye left 

 after the boiling process contains all the incrustating parts of the wood used, and, 

 in order to regenerate the alkali salts, the lye is evaporated and the residue is heated 

 red hot or melted. The heated or melted mass is then soaked in water and is 

 boiled, in order to transform the carbonate of soda into soda hydrate with burned 

 lime that is, to make it caustic. The loss of alkali is made up for by addition of 

 soda or sulphate of soda (glauber salt). The latter is generally used neutral; but 

 by treating the cheap, sour sulphate of soda, which is obtained as a by-product in 

 the manufacture of nitric acid, with the carbonate of lime obtained by the above- 

 mentioned regenerating process, or by adding it to the lye not made caustic, such 

 sour sulphate of soda can also be used. 



The sulphite method has an advantage over the alkali method in this, that the 

 former yields at least 10 per cent more pulp, and the pulp produced can also with- 

 out special bleaching be used for ordinary printing paper and possesses great com- 

 pactness. The sulphite pulp has been compared to the hard, smooth, and nonelastic 

 flax fiber, while the alkali pulp reminds one more of the soft and elastic cotton fiber, 

 which is so susceptible of coloring. While the alkali pulp is thus suitable for col- 

 ored paper, the sulphite pulp is better adapted for writing and printing paper. 



An important question in determining the value of wood pulp is the moisture. 

 Wood pulp is often sold containing 50 to 60 per cent of moisture, and in many 

 places the custom is to base the price on 50 per cent air-dried pulp. The amount 

 of moisture in air-dried pulp is considered to vary between 10 to 12 per cent, ac- 

 cording to the agreement between seller and purchaser; but this often gives cause 

 to controversy, and it would be better to base the price on absolutely dry pulp. 



By an extensive series of experiments, it has been learned that absolutely dry 

 chemical pulp absorbs less than 10 per cent moisture from the atmosphere, while 

 mechanical pulp can absorb 11.58 per cent. The Norwegian and Swedish Cellulose 

 Pulp Association has fixed 12 per cent as the limit of the allowable moisture of air- 

 dried pulp; that is, 100 kilograms of air-dried cellulose should contain 88 kilograms 

 of absolutely dry pulp and 12 kilograms of water. 



The most important raw material for wood pulp in Sweden is spruce, but aspen 

 and pine have also been used to a smaller extent. 



From wood pulp are manufactured household goods, such as pails, tubs, and 

 kitchen utensils; doors, furniture, bodies of carriages, ornaments for ceilings, pic- 

 ture frames and moldings, artificial leather, cordage, textile fabrics, and nitric gun- 

 powder. Felt for use as surgical bandages is also manufactured from chemical 

 pulp, which is made antiseptic by saturating the felt in different solutions, such 

 as corrosive sublimate, boracic acid, etc. 



It has recently been stated than an imitation of silk fiber is made from wood 

 pulp. By proper treatment the pulp is dissolved and by a special apparatus pressed 

 through very fine glass tubes, water being used to make the threads retain their 

 shape after having been formed by said apparatus. 



The most common method of manufacturing the chemical pulp at the present 

 time in Sweden is the calcium-sulphite method. Some factories are using the soda- 

 sulphate method. 



