80 Intelligence and Miscellaneous Articles. 



than with distilled water ; but nevertheless very frequent retarda- 

 tions of 10°, 15°, and more are seen, as in preceding experiments. 



The presence of platinum, and in general of metallic substances, 

 is known to have the reputation of hindering retardations of ebul- 

 lition in glass vessels ; and for a long time platinum wires have 

 been used in concentrating liquids to prevent them from jumping 

 over. Platinum wires placed in distilled water hinder, in fact, these 

 retardations from being produced when, after having been heated 

 once or twice to 100°, water is subjected to a diminution of 

 pressure. But if the liquid containing platinum wire is heated to 

 boiling for several times, and then allowed to cool — if especially 

 platinum is for some days in contact with water at the bottom of 

 the vessel, it is soon seen that the metal has become inactive, and 

 then delays are observed as considerable as if water alone were in the 

 retort. If ordinary water is taken abundantly carbonated, if along 

 with it various solid bodies are introduced, facts are observed ana- 

 logous to that which has been mentioned in the case of platinum. 

 I have tried pieces of iron, lead, tin, zinc, copper, &c. ; fragments 

 of chalk, of wood, of quartz, paper, &c. In the first reheating, the 

 presence of these bodies prevents any retardation, and ebullition 

 takes place at the exact point at which the temperature of the liquid 

 imparts to the vapour an elastic force equal to the superficial pres- 

 sure. But if they are left for some time in contact with water, 

 heated four or five times to ebullition, the contact of all these bodies 

 appears to have become indifferent, and the liquid furnishes then 

 very frequent examples of the retardation of ebullition. The fol- 

 lowing are some examples in which the retort contained ordinary 

 water, with fragments of iron, platinum, lead, chalk, and wood : — 



mm. 



74 217 68-5 



85 171 63-2 



67 71 45 



72 87 49. 



These correspond to retardations of 5°'5, 21°'8, 22°, 23°. Ebul- 

 lition then commenced, sometimes spontaneously, sometimes by 

 a blow given to the vessel; it was always very tumultuous and 

 violent, almost explosive. 



These facts and others relative to other liquids, show that the 

 ordinary law regarding the boiling-point of a liquid in reference to 

 its pressure can only apply when ebullition is arrived at by a change 

 in pressure rather than by a variation of temperature. These facts 

 show, moreover, that water is susceptible of presenting great re- 

 tardation in its ebullition, even when in contact with any metals 

 and solid substances. Glass and porcelain vessels form by no means 

 an exception. Lastly, it is seen that the contact of solids is some- 

 times active and sometimes indifferent; and by analyzing the expe- 

 riments of which I have given extracts, it is soon seen that the very 

 probable cause of this change of influence is the presence or absence 

 round these solids of a more or less condensed gaseous atmosphere. 

 — Comptes Rendus, May 30, 1864. 



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