May 190?.] 



287 



Timbers. 



Wood pulp is now used for the manufacture of nitro-cellulose, For ex- 

 plosives the pulp has to be of a special nature. It is also used under! the name of 

 ''Cellulose Wadding," prepared under Feirabetid's Patent No. 3061, where it replaced 

 cotton wool for surgical bandages, giving most excellent results. It is also, as Pfuhl 

 reminds us, coming into use in the form of paper in narrow strips, which are after- 

 wards spun into filaments woven into garments, such as under Kellner-Turq processes 

 and theSilvaline yarn process. Then, of course, it is used in considerable quantities 

 now for manufacture of artificial silk. According to the Stern process, it is con- 

 verted into viscose by Cross, Bevau and Beadle's process, and then spun into fine 

 portions through a special solution from which it emerges in the form of filaments. 

 For this product the inventors— all three British by the way — were awarded the Grand 

 Prix at the last Paris Exhibition. They have also received numerous other valuable 

 awards. 



In America, where they have no esparto, the printing papers for process 

 blocks can be produced by the aid of aspen, which fibre under the soda process 

 makes a good substitute for esparto. I think, perhaps, not sufficient attention has 

 been paid to the subject of the great differences in the qualities of papers made from 

 wood pulp according to the kind of pulp used and the process adopted. Thus, on 

 the one hand, Ave were able to produce soft and spongy papers, excellent for filter 

 papers, and, on the other hand, imitation parchments from Mitscherlish pulp, close, 

 transparent, grease-proof, the latter being produced by the aid of the basalt lava 

 beater roll. 



Then we have the milk of lime process, whereby bi-sulphite of lime is now 

 produced by passing the fames of sulphur through milk of lime instead of by 

 allowing it to pass up towers filled with limestone, which is the general system in 

 use in Sweden and Norway. The liquor made by the milk of lime process is identical 

 with that of the ordinary method, but it has the great advantage that it produces a 

 solution of absolute uniformity in strength, a difficult thing with the limestone, 

 but a very important thing for ensuring regularity in the cook. 



Digester Linings. 



One of the most important things in the history of wood pulp has been the 

 question of digester liuings. The Mitscherlich lining in 1891 consisted of tarred pitch 

 to protect the shell, then a layer of thin sheet lead, and on top of these two courses 

 of specially acid-resisting bricks, formed with tongue and groove, cement being used 

 sometimes with the bricks. Some foreign mills place the lining of lead between the 

 two cou-ses of bricks. In a digester heated by indirect heat, a coating of the 

 sulphite of lime cau be produced on the surface, which gives a protection for the 

 metal. Jungend Lindig used the coating of double silicate of lime and iron. Kellner 

 took out numerous patents for cements, consisting either of ground slate and 

 silicate of soda, or powdered slate and glass and Portland cement. One of the 

 earliest, and one of the most successful, linings was prepared by Wenzel, consisting 

 of a special cement, for the most part a manufacture of Portland cement and silicate 

 of soda, set in blocks in wooden moulds made to conform to the shape of the digester. 

 Finally, excellent results were obtained by the use of Portland cement alone, which 

 in many cases is reinforced by a facing of special brick or tile, the usual thickness of 

 the cement lining being 4 in. All cement liuings are more or less porous when 

 applied, but in use soon fill up with sulphate and sulphite of lime. After numerous 

 years of work, a great many failures, a great many patents, lawsuits, and infringe" 

 ments, a brick has been introduced for lining which answers the purpose. Until a 

 suitable lining could be devised, the sulphite process could not be regarded as a 

 success. As the early troubles with the linings made it impossible to make pulp 

 yheaply, and the corrosion of the shell contaminated and discoloured the pulp, mostj 



