CHEMISTRY. 213 



and are given off from it. This action does not take place if the 

 body introduced has previously been made chemicall}^ clean, nor 

 will the body introduced continue to promote the action indefi- 

 nitely if the liquid is of such a nature as to render it clean after a 

 time. 



*' It has been recommended to use sharp-pointed or roughened 

 bodies, under the impression that steam is given off with greater 

 facility from the points or the teeth. This is a mistake. Make 

 these rough or sharp-pointed bodies clean, and they cease to act. 

 Sharp, angular fragments of glass, washed in suli^huric acid and 

 rinsed, no longer act as nuclei. A rat's-tail file passed through 

 the flame of a spirit lamp also becomes denucleized. A bod}' such 

 as a file is apt to collect between its teeth the greasy kind of mat- 

 ter that acts so well as a nucleus; and this has led to an idea in 

 favor of rough bodies. The air is not a nucleus. When Dr. Bos- 

 tock, in his experiments, found his thermometer cease to act, and 

 by taking it out of the liquid and waving it in the air it liberated 

 vapor when restored to the liquid, the thermometer had caught 

 from the air some unclean particles of dust, which acted for a 

 moment as nuclei, until, by the action of the ether, they became 

 denucleized." 



Looking, then, at the matter from a practical stand-point, what 

 is wanted in conducting the processes of boiling and distillation is 

 a body which will act permanently as a nucleus. Such bodies are 

 charcoal, coke, pumice-stone, meerschaum, and a few others, 

 which act by virtue of the powerful force of capillarit3^ The same 

 force which, according to Saussure, enables one volume of box- 

 wood charcoal to absorb 90 volumes of ammoniacal gas, 85 of 

 hydrochloric acid gas, 65 of sulphurous acid gas, and so on, ena- 

 bles these porous bodies to absorb vapor from boiling liquids, and, ' 

 under the continued action of the heat, to give it out in never- 

 ceasing jets, thus relieving the vessel of all tendency to bumping, 

 making the boiling soft, gentle, and regular, and increasing the 

 quantity of the distillate. Charcoal made from cocoa-nut shell 

 answers best for this purpose. Thus, methylated spirit of wine, 

 boiling at 171° F., was distilled in a glass retort. The amount of 

 distillate collected in a given time was weighed, and bore to 

 the amount collected in the same time after the addition of a few 

 fragments of cocoa-nut shell charcoal, the ratio of 100 : 133. Even 

 a short bundle of capillary glass tubes, united like a fagot by a 

 thread in the middle, is an active nucleus in liberating vapor. 

 Such a bundle, vveiging only 10 grains, put into a retort from 

 which methylated sj^iwt was being distilled, raised the amount of 

 distillate in the ratio of 100 ; 110. — Tomlinsoiiy Lecture before 

 Chem. Soc. 



ACTION OF BOILING LIQUIDS UPON GLASS AND PORCELAIN 



VESSELS. 



Dr. A. Emmerling publishes (*' Ann. Ch. ii. Ph.," June, 1869) 

 the results of a series of extended and carefully conducted experi- 



