^^ DIVEES AND HAUA. 



significance, since Fremy und, after him. Clans have represented the 

 dipotassium salt to contain three atoms of hydrogen instead of the one 

 given by the imide constitution and displaced by metal in the normal 

 salts. But careful combustion of some grammes of the dried salt with 

 copper oxide gave us in one case only 0*22 per cent., and in another 

 only 0*24 per cent, of water, calculated from the hydrated crystals, and 

 such a percentage corresponds to only about one-ninth of an atom, 

 instead of the extra two, of hydrogen required l)y the sulphammonate 

 constitution given by Claus. 



When dried trisodium imidosulphonate is heated somewhat 

 strongly in an open tube it yields, with fusion and effervescence, 

 nitrogen and some sulphur dioxide, and sulphur whicli sublimes. 

 The saline mass becomes also very dark-coloured from the presence in 

 it of sulphur, and gradually solidifies, until at a commencing red -heat 

 it forms a semi-fused hepar sulphiiris. By heating in a vacuum, proof 

 is obtained that the sulphur dioxide comes only from the action of 

 the air upon the sulphur. From 350° to 440,° gas of only very 

 low tension is given off, along with sulphur vapour forming a sub- 

 limate of drops. Just below the softening point of good soft lime- 

 glass, the salt fuses and efi'ervesces. The gas consists entirely of 

 nitrogen. Some of tlie sulphur remains in the fused mass, partly free, 

 partly as thiosulphate. A trace of the ammonia compound with 

 sulphur dioxide forms a sublimate. Apart from this the reaction is 

 expressed by the equation- — 



2NaN(S03Na)2=N2-|- Ö -1- 8 SOiNag 



Acids readily dissolve trisodium imidosulphonate, yielding neutral 

 solutions of the disodium salt when the quantity of acid is equivalent 

 to one-third of the sodium. Remarkable is the action of concentrated 

 sulphuric acid which, being not in excess, dissolves the crystals with 

 marked fall of temperature, although when in quantity more than 



