132 Botanical Report. 



works. The liquor was a very concentrated one, having a specific gravity 

 of 1.342, and was certified as being as free from salts of iron as was obtain- 

 able, having been evaporated to a greater degree of concentration than 

 usual, so as to remove all the copperas possible. The thorough separation 

 of the salt of iron is, however, a difficultly obtainable result, since the two 

 sulphates occasionally combine and form a double salt. On analysis it was 

 found still heavily charged with protoxide of iron, containing fully six 

 ounces of the anhydrous protosulphate in each imperial gallon. The 

 inevitable peroxidation of this quantity would no doubt have discoloured 

 the paper. On concentrating the solution to a slightly greater extent 

 than received, in the endeavour to deposit a further portion of the iron 

 salt, the whole liquor solidified on cooling, so that this anticipated source 

 of alumina had to be set aside. 



For the purpose of making trial of acetate of alumina as a substitute 

 for alum, in the rosin-sizing process, without regard to economy, a quantity 

 of the acetate was prepared from pure acetate of lead and alum. The 

 proportions required for the perfect decomposition of these two compounds 

 were found by experiment to be, 500 of the lead salt, to 315 of alum, or, 

 stated in more practical proportions, 5 lbs. of the former to 3 lbs. 2 oz. of 

 the latter, 3 gallons of water being employed, and the addition of 2 oz. of 

 crystallised carbonate of soda to the materials after their mutual decom- 

 position. These proportions are somewhat different from those generally 

 adopted by calico printers and others, in the preparation of acetate of alumina 

 from this soui'ce. The result of the application of the acetate of alumina 

 so prepared, was a paper more thoroughly sized, and consequently heavier 

 sized, than by any process previously in use, and the paper answered the 

 purposes of the printer equally well. It, however, softened slightly in 

 moist states of the atmosphere, owing to the presence of the deliquescent 

 acetate of potash, from the use of alum in the preparation of the acetate. 

 The influence of the weather on the paper so sized, was less than on a 

 quantity prepared by using " concentrated or patent alum," a substance 

 now being experimented with at some paper manufactories, as at Dickin- 

 son's in London. This patent alum, on analysis, was found to be principally 

 composed of sulphate of alumina with a small proportion of soda salts. 

 From the results of the experiments with the acetate of alumina, its use 

 in the sizing prosess would, Mr. Macadam anticipates, be found worthy 

 of the attention of paper manufacturers, were an economical and pure 

 source of alumina at command. 



The following report was read : — 



19th December, 1849. — Botanical Report. 



At a meeting of the Botanical Section on the 11th instant. Dr. Walker 

 Arnott made some observations on two American trees, exhibiting an 

 anomalous mode of growth. Mr. Keddie reported that the Botanical 

 Section had elected the same office-bearers as last year. 



