CHEMICAL SCIENCE. 249 



quantity sufficient for the neutralization of the whole, or a part of the alkali 

 of the resin size which is used. The quantity or proportions of acidulous solu- 

 tion, when free acids are employed, is accurately determined by alkalimetri- 

 cal processes ; and such acid solutions are added to the paper pulp either be- 

 fore or after the addition of the resinous size. In carrying out the invention, 

 the aid of single sulphates, or other binary compounds in the form of aqueous 

 solutions, and suited in quantity to the alkali present in the size, are used. 

 Paper produced under this system of treatment is peculiarly well-suited for 

 printing by lithography or from engraved plates, as it possesses an absorbent 

 surface of a uniform character. It has also a less injurious effect upon the 

 engraver's plates, and is well-suited for letter-press printing, as it is readily 

 susceptible of uniform damping, and affords a clear impression. The follow- 

 ing is a detail of the materials used and the plan followed : 



In the preparation of the resin size, as ordinarily used, the resinous matter 

 is dissolved through the medium of water by alkaline compounds, carbonate 

 of soda, or carbonate of potash, for example. "When alum is added to such 

 solution in contact with the paper pulp, decomposition of the size-solution 

 takes place ; the acid of the alum neutralizes the alkali which is present, and 

 the resin is precipitated in contact with the fibrous matter of the paper pulp. 

 In sizing with resin the antiseptic influence of alum is not required, as in the 

 case of sizing paper by the agency of animal matters ; or if at all necessary, it 

 is only so within a very limited extent. The invention, therefore, essentially 

 consists in the application and use of the free acids, or single sulphates, or 

 other binary compounds, by the agency of which the desired neutralization of 

 the alkali of the size-solution is secured in a more economical manner, and 

 with superior results as regards the quality of the paper, than when the chem- 

 ical effect arises soleh' from the use of alum in the ordinary way. The agents 

 named are employed to a greater or less extent, in accordance with actual cir- 

 cumstances, introducing at the same time more or less alum as may be advis- 

 able. When single sulphates are used to effect by their continued action the 

 neutralization of the alkali of the size-solution, they are applied in accurate 

 atomic proportions. The size-solution is constantly prepared from the same 

 proportions of resin, water, and alkaline compounds, so that whether commer^ 

 cial carbonate of soda or potash, or soda ash be used, the proportion of alkali 

 in a given measure of the size-solution may be as constant within such narrow 

 limits, as any fluctuations in the per centage of alkaline value of such com- 

 pounds will admit. The strength of the acid aqueous solutions is constant. 

 Thus, taking sulphuric acid as an example, it is employed as an aqueous solu- 

 tion, having a strength of 20 by Twaddell's hydrometer. While this strength 

 is convenient for regulating and measuring the required quantities, the degree 

 of dilution is otherwise unimportant It is advisable, however, to make this 

 the minimum amount of dilution. 



The requisite of the dilute acid is regulated as follows : The size-solution 

 being constant, or nearly so, in alkaline strength, and being used in definite 

 and constant quantity for each class of paper, as sized in any particular engine 

 of the paper-maker's works, according to the capacity of such engine, a pre- 

 liminary experiment is made to ascertain, by means of a graduated tube (di- 



11* 



