1844.] of Bodies generally existing as Gases. Ill 



rature of 75 below 0, and the solid portion was heavier than 

 the liquid. 



When in the solid state it gives off so little vapour, that the 

 eye is not sensible of its presence by any degree of colour in 

 the air over it when looking down a tube 4 inches in length, 

 at the bottom of which is the substance. Hence the pressure 

 of its vapour at that temperature must be very small. 



Some hours after, wishing to solidify the same portion of 

 euchlorine which was then in a liquid state, I placed the tube 

 in a bath at 1 10, but could not succeed, either by continuance 

 of the tube in the bath, or shaking the fluid in the tube, or 

 opening the tube to allow the full pressure of the atmosphere ; 

 but when the liquid euchlorine was touched by a platinum wire 

 it instantly became solid, and exhibited all the properties before 

 described. There are many similar instances amongst ordinary 

 substances, but the effect in this case makes me hesitate in con- 

 cluding that all the gases which as yet have refused to solidify 

 at temperatures as low as 166 below 0, cannot acquire the 

 solid state at such a temperature. 



Nitrous Oxide. This substance was obtained solid by the 

 temperature of the carbonic acid bath in vacuo, and appeared 

 as a beautiful clear crystalline colourless body. The tempera- 

 ture required for this effect must have been very nearly the 

 lowest, perhaps about 150 below 0. The pressure of the 

 vapour rising from the solid nitrous oxide was less than one 

 atmosphere. 



Hence it was concluded that liquid nitrous oxide could not 

 freeze itself by evaporation at one atmosphere, as carbonic acid 

 does ; and this was found to be true, for when a tube containing 

 much liquid was freely opened, so as to allow evaporation down 

 to one atmosphere, the liquid boiled and cooled itself, but 

 remained a liquid. The cold produced by the evaporation was 

 very great, and this was shown by putting the part of the tube 

 containing the liquid nitrous oxide, into a cold bath of carbonic 

 acid, for the latter was like a hot bath to the former, and 

 instantly made it boil rapidly. 



I kept this substance for some weeks in a tube closed by 

 stopcocks and cemented caps. In that time there was no 

 action on the bitumen of the graduation, nor on the cement of 

 the caps ; these bodies remained perfectly unaltered* 



