70 HE PORT— 1876. 



On the Prevention of the Pollution of Rivers. By Hev. R, Thomson. 



On the Growth of Mildeiv in Grey Cloth. By William Thomson, F.R.S.E. 



The author described the size vised by Lancashh-e manufacturers, which is nearly 

 always more or less strongly acid. 



Two series of experiments on the relative actions of salts, often added by manu- 

 facturers to their size, in aiding or retarding the development of mildew, showed 

 that the free acid present, together with dampness, is the most fruitfid cause of 

 mildew ; and if the acid be neutralized with soda ash, mildew develops with much 

 difficulty, and only after a very considerable lapse of time. 



On the Nitroso Derivatives of the Terjyenes. By "VV. A. Tilden, D.Sc. 



Preliminary Note on a new Iso-purpunne. By W. A. Tilden, D.Sc. 



On the Prevention of Fraudulent Alterations in Cheques cj'c. By F. Ward. 



On the Means of Suppressing Alkali Waste: By Walter Weldon. 



New Cotamine Derivatives. By C. E. Alder Wright, D.Sc. 



When dilute bromine water is added to a solution of cotarnine hydrobromide 

 combination takes place, and a crystalline orange precipitate is thrown down con- 

 sisting principally of dihrom-hydrocotai-nine hydrohrumide ; if excess of bromine be 

 used, the precipitate chiefly consists of tribrom-hydrocotarnine hydrobromide, these 

 two brommated bodies being formed thus : — 



Cotarnine. Dibrom-hydrocotarnine. 



C,, H,3 NO3, H Br+Br, = C,, H,3 Br, NO3, HBr. 



Tribrom-hydrocotarnine. 



Ci, Hj3Br2 NO3, HBr+Br, = H Br+C,, H^, Br, NO3, HBr. 



If hydrocotaruine hydrobromide be used instead of cotarnine hydrobromide, and 

 excess of bromine be added, the same tribrom-hydrocotarnine hydrobromide is 

 formed, thus : — 



Hydroootarnine. Tribrom-hydrocotarnine. 



Oi, H,5 NO3, HBr-|-3Br,=3H Br-f C^, HijBr,^ NO3, HBr. 



Dibrom-hydrocotarnine hydrobromide loses the elements of hydrobromic acid, 

 forming bromocotarniiie hydrobromide on boiling with water, aqueous caustic potash, 

 or alcoholic silver hydrate, thus : — 



C,, Hi3 Br, NO3, HBr=HBr-l-C„ H,, BrXOj, HBr. 



The bromocotarnine thus formed resembles cotarnine in many respects ; its salts 

 are crystallizable and very soluble ; the base when crystallized from ether is repre- 

 sented by CijHaBrNOj, H^O, the associated water being lost at 100° with partial 

 decomposition just as with cotarnine. When heated to about 180°, hydi-obromic 

 acid is evolved ; the residue contains a blue product insoluble in boiling alcohol, ben- 

 zene, chloroform, petroleum, turpentine, carbon disulphide, and ether, but sparingly 

 soluble with a brilliant blue colour in boiling glacial acetic acid, glycerine, or 

 aniline, and readily soluble in cold concentrated sulphuric acid to a most intensely 

 colom-ed magenta liquid : the colorific povt'er of this bodj' is most remarkable, a 

 minute speck scarcely visible ginng a deep coloration to a considerable bulk of 



