Mk. JIacadam on the Paper Manufacture, 127 



and yields crystals of common salt when treated with the same acid. It 

 is thus associated with Wollastonite, or soda-table spar, a mineral occur- 

 ring in the Bishopton tunnel, and in the Kilpatrick hills." There is 

 however this difference between the two cases, that in the localities last 

 mentioned the mineral has no direct connection with limestone, although 

 calcareous spar occurs abundantly ; whereas at Innerkip, it has obviously 

 originated in a change induced upon common limestone. 



The following communication was made : — 



XVI. — Observations and Experiments on the Paper Manufacture, with 

 some Improvements on the usual process. By John Macadam, 

 Lecturer on Chemistry. 



The author first gave a condensed statement of the process of paper 

 making, especially of those varieties used as printing papers, and which 

 are rosin-sized. His descriptions were illustrated by suitable diagrams, 

 specimens and experiments. Mr. Macadam then referred to various 

 applications of Chemistry to this important branch of manufacture, and 

 certain improvements he had effected on the customary process. The 

 processes and improvements detailed had reference to the paper factories 

 of Messrs. Alexander Duncan & Son, of the Herbertshire Mill, Denny, 

 and Messrs. R. & J. Couper of Cathcart ; and for obvious reasons are 

 here referred to, in a partial and abridged form. 



Under the chemical part of the subject, the soda-ash used in the 

 cleansing of the crude rag was first treated of. Soda-ash appears to have 

 been employed in paper works in a partially or totally undecarbonated 

 state. The alkaline solutions in use were therefore far from being econo- 

 mically prepared. Caustic soda ley had been found more effectual and 

 economical. The proportions recommended for its preparation were 121, 

 lbs. of soda-ash, containing 44 to 48 per cent, of alkali, 100 lbs. of best 

 caustic lime, and 150 gallons of water. The proportion of water stated is 

 sufficient, if maintained throughout the preparing process, to prevent the 

 after decomposition of carbonate of lime by concentrated leys, noticed 

 by Liebig. The proportion of lime is higher than the theoretical quantity, 

 but was found in practice to yield a thoroughly caustic ley when waste 

 steam was the heating agent, a source of heat very generally at command. 

 The usual precautions adopted in laboratories, as the boiling of the ash in 

 water, with the addition of the lime in the state of a creamy paste, in suc- 

 cessive portions — the boiling of the soda solution between each addition of 

 lime — the supplying of the loss of water by evaporation, and the covering 

 up of the material when made, were enforced. Some apprehension existed, 

 that the soda, in its caustic condition, might act too energetically on the 

 rag.?, injuring the finer fabrics, and causing the stronger portions to 

 become ropy, and conscfjuently more difficult afterwards to reduce to the 

 state of pulp. This was obviated by using the solutions at much lower 



