514 PAPER MAKING. 



Ammonia Company's" works, and already forms an indispensable 

 adjunct to a thriving paper mill. What is "ulmate of ammonia?" Dr. 

 Playfair describes it as the powder of woollen fibre, separated from 

 muslin-de-laines by the action of high -pressure steam. Mixed cotton and 

 wool fabrics are, unless specially treated, worthless as rags .to the paper- 

 maker. There have been practised two modes of separating the cotton and 

 the wool, either at the expense of one or the other. Thus, if it were desired 

 to obtain the wool, the rags of the mixed stuff were steeped in acids 

 which decomposed the cellulose of the cotton, changing it into sugar, 

 which was dissolved and lost in the process. To save the cotton, on the 

 other hand, the rags were steeped in a strong alkali, which, acting upon 

 the wool, formed a soapy compound in which the cotton remained intact. 

 Now Mr. Ward, while separating the cotton fibre in a condition serviceable 

 to the paper-maker, has contrived to retain the wool in a condition fit 

 for something — manure, at least. He subjects muslin-de-lain e, or the 

 rags of mixed cotton and wool stuffs, to the action of steam of 50 lb. 

 pressure or so, the effect of which is to convert the wool into a brittle, 

 bituniinoixs, or resinous matter, which separates readily, as a powder 

 from the cotton. 



The importance of this process will justify us in quoting at some 

 length from Mr. Ward's specifications. 



His improvements, patented in 1857, were intended to remedy the 

 defects of the 'wet process' of separation, and to accomplish more 

 economically and completely the separation of the azotised from the 

 unazotised ingredients of the mixed materials. 



In carrying this invention into effect Mr. Ward employs a closed 

 boiler or digester, of any convenient form and size, preferring a cylin- 

 drical form with hemispherical ends, set with its long axis vertical, and 

 having sufficient capacity to hold a ton of mixed rags. This digester has 

 the usual fittings. There must also be provided, either in the structure of 

 a digester itself or as part of the apparatus used therewith, suitable 

 appliances to protect the materials under treatment from the injurious 

 action of condensation water in excess. These appliances may vary, 

 but the form preferred consists in an inner case or cradle, rather less in 

 height and diameter than the cylindrical portion of the digester, into 

 which it may be let down, and from which it may be lifted out by 

 means of a crane. 



The sides of this case or cradle should be perforated with numerous 

 holes to admit steam, but its lid and its lower part should be imper- 

 forated: the object of the ca.se or cradle being to hold the materials 

 under treatment and to protect them from the contact of any condensa- 

 tion water that may be formed in the interior of the digester and run 

 down its sides, or accumulate at the bottom, or drip from the lid. 



To obviate, as much as possible, loss of heat by radiation, which 

 involves formation of condensation water (and, consequently waste of 

 fuel), the digester should be carefully clothed with non-conducting 

 material. 



