130 Mk. Macadam on the Paper Mamifucture. 



kind of pvdp, were also prepared and at hand, to serve as a check upon 

 the contents of the engine, when charged according to the fixed scale of 

 measures. 



Mr. Macadam further referred to the late introduction of Antichlore, 

 or sulphite of soda, for the purpose of removing any remaining traces of 

 chlorine from the pulp, after being washed with water in the engine, 

 subsequent to the bleaching process. The chemical action of this useful 

 de-chloridising agent, under such circumstances, may be thus repre- 

 sented — 



NaO SO,, + CI + HO,=NaO SO3 + HCl. 



In reference to rosin-sizing, — The proportions which had been found 

 most suitable for the preparation of rosin-size were 42 lbs. of crystallized 

 carbonate of soda, 80 lbs. of rosin, and 60 gallons of water. The materials 

 are heated in a water, in preference to a steam bath, and when dissolved 

 are further diluted with 120 gallons of hot water. The solution thus 

 obtained has a specific gravity of 1.014, and is strongly alkaline to test 

 papers. Though slightly milky to appearance, the liquid is completely 

 filterable through bibulous or unsized paper, indicative of the total solution 

 of the rosin present. This dissolved state of the rosin was further corro- 

 borated by there being no deposition of solid matter on the exposure of the 

 filtered liquid. The size was, moreover, not decomposed, or its dissolved 

 condition disturbed by extensive dilution with water, as might be anticipated 

 from its having the constitution of a soluble soap. The size so prepared 

 was extremely susceptible of decomposition on the addition of very dilute 

 acids or solution of acid salts, as alum, and was completely clarified when 

 treated with very dilute alkalies. These reactions showed that the size 

 was in the best condition for its intended use, viz. for the precipitation of 

 the rosin, on being brought in contact with alum in a very diluted form 

 in the engine, so as to size the pulp. Though this decomposition of the 

 size and precipitation of rosin, on the addition of alum, is ultimately 

 necessary for the sizing process, still, it is an important point for considera- 

 tion, which should precede the other, the alum or the size ? or, under 

 what circumstances the deposition of the solid matter would prove most 

 advantageous and effective for the sizing of the paper ? This, in reference 

 to rosin-size, where no antiseptic influence is necessary, seems to have 

 been an open, and, apparently, an indifferent question. Dr. Ure and 

 others describe them as being mixed together before adding either to the 

 sizing engine. Many manufacturers, as the Herbertshire Mill Company, 

 placed the rosin-size in the engine first, and subsequently the alum ; a 

 system quite right in principle if the size were of animal origin, and 

 required the presence of excess of an antiseptic agent, as alum, to prevent 

 any after decomposition. Veiwing, as the author did, the alum, when 

 acting in rosin-sizing, as similar to a mordant in dyeing with adjective 

 colouring matters, it was presumed that the alum should precede the size. 

 This opinion was confirmed by the results of two experiments, viz. : — 



