334 HEATS OF FORMATION OF THE CYANOGEN SERIES. 



spiral and phial, into the calorimeter, the water in which should 

 completely cover the two points of the phial. We, however, 

 keep the lower point from touching the bottom of the calori- 

 meter, so as to prevent the possibility of its getting broken in 

 the course of the subsequent operations. When these pre- 

 parations are completed, we break the upper point of the phial, 

 by a sharp blow with a platinum hammer against a piece of 

 glass resting on this point, or in some similar way ; but the 

 lower point must be carefully kept intact. Under these con- 

 ditions, cyanogen chloride is at once given off, escaping in 

 gaseous bubbles from the broken point ; these are absorbed, as 

 they appear, by the alkaline solution. The operation proceeds 

 with extreme regularity, if all the prescribed precautions have 

 been observed. 



Nevertheless, we follow at each minute the course of the 

 calorimetric thermometer. At the end of about 20 minutes, 

 the vaporisation is complete and the maximum temperature 

 attained. It exceeds the original temperature by about 2. 

 The phial is then completely broken up with the hammer, in 

 order to destroy the last traces of cyanogen chloride, and 

 complete the mixture. 



The first stage of the operation converts the cyanogen 

 chloride into potassium chloride and cyanate (or rather 

 isocyanate), mixed with a certain quantity of potassium and 

 ammonium carbonates. 



The proportion of these products of a further reaction varies 

 according to the concentration of the potash and various other 

 circumstances ; it seems to increase little by little, by a slow 

 reaction. We cannot, therefore, stop at this point, as it does not 

 furnish a reliable basis for calorimetric computations. 



Second stage of the experiment. This is why, when the 

 maximum has been reached and the phial broken, we introduce 

 into the calorimeter a certain quantity of dilute hydrochloric 

 acid, rather more than would be required to exactly neutralise 

 the potash used in the experiment The temperature of this 

 acid is, moreover, obtained with exactness by special measure- 

 ment. A new reaction is immediately developed ; a reaction 

 which rather rapidly, but not instantaneously, converts the 

 potassium cyanate (iso-) into potassium chloride and carbonic 

 acid in solution. In order to avoid the liberation of this last 

 gas, in consequence of the liquid being mixed with air, this 

 liquid is agitated by means of a stirrer that moves horizontally 



(P- W7). 



The maximum is attained in six minutes. It exceeds the 

 original temperature by about 3. It lasts three minutes, and 

 then the temperature begins to fall. The progress of this cool- 

 ing is followed during thirty minutes. The actual experiment 

 lasts about as long. 



