94 On the Condensation [1823. 



in which liquid nitrous oxide was afterwards produced, gave the 

 pressure of its vapour as equal to above 50 atmospheres at 45. 



Cyanogen. Some pure cyanuret of mercury was heated 

 until perfectly dry. A portion was then enclosed in a green 

 glass tube, in the same manner as in former instances, and 

 being collected to one end, was decomposed by heat, whilst 

 the other end was cooled. The cyanogen soon appeared as a 

 liquid : it was limpid, colourless, and very fluid ; not altering 

 its state at the temperature of 0. Its refractive power is 

 rather less, perhaps, than that of water, A tube containing 

 it being opened in the air, the expansion within did not appear 

 to be very great ; and the liquid passed with comparative slow- 

 ness into the state of vapour, producing great cold. The 

 vapour being collected over mercury, proved to be pure 

 cyanogen. 



A tube was sealed up with cyanuret of mercury at one end, 

 and a drop of water at the other ; the fluid cyanogen was 

 then produced in contact with the water. It did not mix, at 

 least in any considerable quantity, with that fluid, but floated 

 on it, being lighter, though apparently not so much so as 

 ether would be. In the course of some days, action had taken 

 place, the water had become black, and changes, probably such 

 as are known to take place in an aqueous solution of cyanogen, 

 occurred. The pressure of the vapour of cyanogen appeared 

 by the gauge to be 3*6 or 3'7 atmospheres at 45 F. Its spe- 

 cific gravity was nearly 0'9. 



Ammonia. In searching after liquid ammonia, it became 

 necessary, though difficult, to find some dry source of that 

 substance ; and I at last resorted to a compound of it which I 

 had occasion to notice some years since with chloride of silver*. 

 When dry chloride of silver is put into ammoniacal gas, as 

 dry as it can be made, it absorbs a large quantity of it ; 100 

 grains condensing above 130 cubical inches of the gas ; but 

 the compound thus formed is decomposed by a temperature 

 of 100 F. or upwards. A portion of this compound was 

 sealed up in a bent tube and heated in one limb, whilst the 

 other was cooled by ice or water. The compound thus heated 

 under pressure fused at a comparatively low temperature, and 



* Quarterly Journal of Science, v. 74 ; see also page 18. 



