158 Intelligence and Miscellaneous Articles. 



nide of silver, so as to affect a small piece of copper, which was ra- 

 pidly covered with a coating of silver, which upon drying peeled off. 

 In this case the cyanide of silver was pure, without any salt ; but 

 in subsequent attempts to silver a wire in this way, I have not suc- 

 ceeded, only a very slight deposit taking place, which was not in- 

 creased by long exposure to the influence. 



But in all the cases I tried subsequent to the one first alluded to, 

 the oxide of silver was dissolved in cyanide of potassium. In the 

 course of time bright and minute crystals were formed, transparent 

 and colourless, on a copper coin. Yours truly, 



P. Baddeley, 

 Surgeon-Assistant, Lahore. 



ON CERTAIN PHENOMENA OF FORCED DILATATION OF 

 LIQUIDS. BY M. MARCELLIN BERTHELOT. 



If a somewhat strong capillary tube, closed at one end and drawn 

 out at the other to a slender point, is filled with water at the tem- 

 perature of 28° or 30° Cent. ; if this tube is cooled down to 18°, so 

 as to cause a certain quantity of air to enter it at the open point, and 

 it is then closed, and again heated to 28° and gradually higher, after 

 a certain time the air is completely dissolved. If cooled to 18°, the 

 original temperature at which the tube contained at the same time 

 gas and liquid, it is seen that the water continues to occupy the 

 whole of the internal capacity, and maintains thus an invariable 

 density between 28° to 18°. Its temperature may even be lowered 

 still more. At this moment the least shock or collision, the least va- 

 riation causes the instant reappearance, with a sort of ebullition, 

 a slight noise, and a shock more or less perceptible, of the gas dis- 

 solved in the water. It dilates rapidty, and in less than a second 

 has resumed its primitive volume at 18°. I have made the same 

 observations with the following liquids, selected from all classes : — 

 water, solutions of various salts and gases, solution of soda, various 

 acids, alcohol, eether, acetone, Dutch liquid, essence of turpentine, 

 oil of olives, creosote, sulphuret of carbon, chlorides of metalloids 

 and metals, bromine. Mercury is the only liquid with which I have 

 not succeeded, either in the presence of the air or in vacuo. A 

 bubble of air remained several days in presence of the mercury with- 

 out dissolving, at least completely, and that under pressures of 200 

 to 300 atmospheres, produced by preventing, for that length of time, 

 the dilatation of the mercury due otherwise to an increased tempe- 

 rature of 8° or 10°. 



In these phsenomena there are two things very distinct. 1. An 

 unstable supersaturation of the liquid by the gas, produced under the 

 influence of the pressure. There are numerous examples of this 

 order of facts. 2. A state of forced dilatation of the liquid : the latter, 

 in fact, an instant before the vibration, fills the volume which the gas 

 occupies an instant after conjointly with it, and this volume is the 

 same which the dilated liquid filled on an elevation of temperature 

 of 8 to 10 degrees and more. The variation of density thus produced 

 is enormous ; for water it is equal to -^-^ of its volume at 18° ; for 

 alcohol to =L, for aether to -^. Such an effect would be produced 

 in an opposite direction only by a pressure of 50 atmospheres for 



