356 Mr. George Henry Jackson, 



nurets are the only ones that have been thoroughly ex- 

 amined ; but there cannot be a single doubt as to the exist- 

 eiice of numerous other double cyanurets. 



The following salts were all prepared by mixing the 

 simple cyanurets of which they are composed in atomic pro- 

 portion, taking care at the same time to exclude atmospheric 

 air as much as possible ; the mixed solutions were then 

 evaporated in vacuo with sulphuric acid. I have styled the 

 following salts the Hydrargyro-cyanurets, because they are 

 composed of bi-cyanuret of mercury and the electro-positive 

 cyanurets. 



I. Hydrargyro-cyanuret of potassium is a compound that 

 crystallizes in octohedrons, white and perfectly transparent, 

 from the mixed solution of bi-cyanuret of mercury and 

 cyanuret of potassium ; in order to ascertain the compo- 

 sition of this salt, the following mode of analysis was used : 

 As most of the double cyanurets retain a portion of their 

 water of crystallization with such violence, it can only be 

 completely expelled by employing a temperature sufficient 

 for the decomposition of the salt ; therefore, the following- 

 mode of ascertaining the water of crystallization appeared to 

 me the best : 



10 grs. of this salt (in crystals) were heated in a tube 

 connected by means of a cork with another tube filled with 

 chloride of calcium in small fragments ; the latter weighed, 

 before the experiment, 38*50 grs. ; after sufficient heat had 

 been applied to completely decompose the salt, taking care 

 at the same time that the mercury did not sublime, the tube 

 containing the chloride of calcium was removed from the 

 tube in which the decomposed salt was, and weighed, when 

 it was found that the increase of weight was - 02 grs. ; too 

 small a quantity to be considered as water of crystallization, 

 being most likely water mechanically enclosed within the 

 crystals, for they decrepitate strongly on being heated. 



Very dilute sulphuric acid was then added to the de- 

 composed salt in the tube, and the mixture warmed ; the 

 solution of sulphate of potassa thus obtained was filtered, 

 and the filter well washed with distilled water ; the solution 

 and washings were then evaporated to dryness in a weighed 

 platinum crucible ; the sulphate of potassa was then 

 ignited, and a small quantity of carbonate of ammonia was 



