1826.] 



Scientific Notices — Miscellaneous. 



157 



Before commencing his investigation, Prof. H. determined in 

 the first place the dilatation of the glass which he employed in 

 the com'se of his experiments. His results, particularly in the 

 two extremes of temperature, differ considerably from those of 

 Lavoisier and General Roy ; on which account we consider it 

 worth while to insert them here. 



14. Prof. Oersted on a Method of accelerating the Distillation of 



Liquids. 



In Gehlen's Journal fur Chemie und Pbysik, i. 277 — 289, I 

 have related a few experiments which demonstrate that the dis- 

 engagement of gas in a fluid, resulting from chemical decompo- 

 sition, never takes place except in contact with some solid body. 

 This principle may without doubt be applied to the disengage- 

 ment of vapours. If a metallic wire be suspended in a boiling 

 fluid, it instantly becomes covered with bubbles of vapour. 

 Hence it might be concluded that a large number of metallic 

 wires, introduced into a fluid which we wish to distil, would 

 accelerate the formation of vapours. To prove this opinion, I 

 introduced 10 pounds of brass wire, of one-fifth of a line in 

 diameter, loosely rolled up, into a distillatory vessel containing 

 20 measures (about 10 pints) of brandy : the result was, that 

 seven measures of brandy distilled over with a heat, which, 

 without the wire, was capable of sending over only four mea- 

 sures. 



An expedient similar to this has been long in common use in 

 England. When a steam-boiler has become encrusted with so 

 much earthy matter that the contained water ceases to boil with 

 rapidity, it is customary to throw in a quantity of the residue 

 obtained from malt by extracting its soluble portion, and which 

 consists chiefly of small grains or fibres. Here the disengage- 

 ment of vapour is piomoted by the large number of thin and 

 solid particles. — (Tidiskrift {^n- Naturvidenskaberne.) 



Prof. Oersted's information respecting the latter method of 

 promoting the generation ol' vapour, was probably derived from 

 a paper by Mr. bald, in tlie Edin. Phil. Journ. vol, ii. p. 340. 

 The material which the engine-keepers of Scotland are in the 

 constant practice of employing to produce this effect, is ndt, as 



