Chemical Apparatus* 123 



bably have got the name of balnea from water 

 being mostly used, which is safest when no 

 great heat is required ; and this is called balneum 

 marice. When sand is used, it is called bal- 

 neum arena. Some have recommended steel 

 filings, and Dr. Lewis quicksilver ; but as quick- 

 silver soon evaporates, I would prefer the softer 

 metals, as bismuth, &"c. It is often found use- 

 ful to make use of air, which is called distilling 

 in copella vacua. The vessel is to be placed in 

 the middle of an iron vessel, suspended by iron 

 hooks, and you must close the iron vessel so as 

 to exclude the external air. The lamp furnace 

 has been used both for the purposes of evapo- 

 ration and digestion. For various hints on fur- 

 naces, see Lewis's Commerce of Arts, and Mr. 

 Nicholson's Dictionary of Chemistry. 



Lutes are commonly used for joining two ves- 

 sels together, and stopping the cavities. The 

 ordinary lutes deserve the name less than others, 

 having no clay in their composition : they are 

 used to stop the junctures of vessels when the 

 heat is gentle ; but it is better to leave a hole 

 made with, a pin than to shut the juncture quite 

 close. Flour and water with gum arabic is good 

 for distilling ; also linseed meal (from which the 

 oil has been expressed) makes a remarkably 

 tight luting. The most convenient linings are 

 bladders cut into slips, and moistened; the in- 

 side of the bladder must be applied next the 



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