Mr. Macadam ow the Paper Manufacture. 131 



Experiment I. — When a portion of bibulous or unsized paper, was folded 

 as a filter, and soaked with the alum as used in sizing, and then the 

 filter, in its wetted condition, filled with size solution as used, the 

 passage of the latter through the filter was not permitted for many 

 hours, and after that, it passed but in a very partial manner. 



Experiment II. — This was conducted as before, only the bibulous paper 

 was soaked with size as used, and the filter so treated filled with 

 solution of alum as used in sizing. The paper, in this experiment, 

 permitted the passage of the alum solution with considerable freedom, 

 the filter being emptied in less than one hour, showing an increased 

 permeability over the previous case. 



These results indicated the order in which the ingredients should be 

 employed, that the alum should precede the size, as the paper pulp, after 

 being saturated with the alum, decomposes the size subsequently brought 

 in contact with it, the solid rosin being deposited within the pores of the 

 fibres, or in close proximity to them. The introduction of the alum first 

 into the engine, was made trial of at the Herbertshire Paper Mill in the 

 beginning of May, last year, half an-hour being allowed before adding the 

 size, and the result was in the highest degree satisfactory. Specimens of 

 paper, sized by both processes, and shown the Society, exhibited a manifest 

 superiority in the manufactured article. As this modification of the 

 customary process has had twelve months' trial, at the rate of 4000 lbs. 

 weight of paper daily, its regularity has been sufiiciently tested. 



In conelusion, as the alum, so far as rosin-sizing is concerned, is only 

 useful in decomposing the alkaline solution of rosin, it appeared to Mr. 

 Macadam that a more economical agent might be employed, which, whde 

 it combined equal safety to the pulp, would prevent the passage of salts 

 of potash into the paper. From the results of a few experiments, acetate 

 of alumina appeared to bo a suitable substance, especially as the acetate 

 of soda, which would be formed on the decomposition of the size, is an 

 efflorescent salt under ordinary circumstances, and would have little or no 

 tendency to cause subsequent dampness in the paper. Besides, any slight 

 excess of acetate of alumina remaining in the pulp would, in most part, be 

 decomposed, with precipitation of alumina, by the temperature of the heated 

 cylinders attached to the machine, and over which the paper passes when 

 being deprived of moisture. The red liquor of commerce offered itself as 

 a cheap and abundant source of this compound ; but, on examination, it was 

 found incapable of serving the intended purpose, from its containing very 

 considerable quantites of oxide of iron and tarry matter. These tinged 

 the size, bestowing upon it a very decided and objectionable colour, while 

 the latter, gave it besides, an unpleasant and persistent odour. The author 

 had some hopes tliat the sulphate of alumina of the alum works, just before 

 its conversion into alum, niiglit be found of sufficient purity to warrant 

 the preparation of an acetate from it, by the addition of acetate of lead. 

 Several gallons of this liquor were therefore obtained from the Campsic 



