1835.] the Advancement of Science, 206 



pyroligneous acid by saturation with lime, distillation and 

 purification by charcoal. He found its boiling point to remain 

 steady at 130°. The following table exhibits its peculiari- 

 ties when compared with pyro-acetic and pyroxylic spirits. 



Sp. Gr. Boiling Point. 

 Pyro-acetic. . , -828 150° 



Pyroxylic . . . -750 140° 



New Fluid . . . -906 130° 



Another fluid was obtained likewise which appeared to 

 be new, exhibiting a strong action with caustic potash. It 

 was suggested, that the first fluid was acetate of methylene, 

 the specific gravity of which is '919 and the boiling point 

 136°. The arguments of Mr. Scanlan were admitted by 

 the Section to be conclusive, in favour of the substance being 

 distinct from pyro-acetic, or pyroxylic spirits. 



22. Mr. Moor mentioned a curious circumstance in refe- 

 rence to the corrosion of lead pipes. The worm of a still used 

 for preparing medicated waters, was exhibited, which was 

 corroded completely through its substance, at those points 

 where it had been supported with wood and tied with twine. 

 At these points a black substance was formed, consisting of 

 oxide and chloride of lead. It was obvious that the effect 

 was to be attributed to galvanic action. 



23. Dr. Barker described a new mode of separating the 

 peroxide of iron by means of acetate of potash. The latter 

 salt, when added to a solution of per-salt of iron, precipitates 

 the peroxide when the liquid is boiled. This would appear 

 to afford an elegant method of separating iron from manga- 

 nese. 



He made an observation relative to the precipitation of 

 magnesia by phosphate and carbonate of ammonia: viz. 

 that the same precipitation takes place with bi-carbonate of 

 potash, and other salts. 



24. Dr. Geoghehan suggested the advantage of employing 

 the double salt of iodide of potassium and bicyanide of mer- 

 cury, for the purpose of detecting muriatic acid in prussic 

 acid. Sulphuric acid is frequently met with in prussic 

 acid, but the distinction between these two acids is readily 

 made, by means of nitrate of barytes. The peroxide of 

 mercury usually employed for testing the purity of prussic 

 acid is ambiguous in its action, as it is usually impure. The 



