1065 



Chemistry. — ''The reciprocal pairs of sails Kd -\- Xa XO^"^ 

 NaCl -{• KN 0^ and the mamtfacture of conversion saipetre.'' 

 By Prof. W. Reinders. (Coinmiinicated by Prof. F. A. H. 



SCHKEINEMAKERS.) 



(Communicated in the meeting of February "28, 1914). 



As is well known we understand by two reciprocal |)airs of salts, 

 the two pairs that can be built up from two difïerent cations and 

 two difTerent anions and can -be converted into each other by doid)le 

 decomposition. 



The instance of tliis mostly quoted is the system : 



KCl + NaNO, ;± KNO3 4- NaCl, 



known b} the technical application of this transformation in the 

 manufacture of conversion salpetre. 



Notwithstanding- the technical importance of this system, a system- 

 atic research as to the equilibria occurring therein was still wanting. 



Hence was started in 1909 by Miss J. Ph. van Rees and myself 

 a research of this kind, which on account of the departure of the 

 first named could not be continued, but has since l)een completed in 

 cooperation with Mr. R. de Lange. The results of these reseai'ches 

 will be communicated here briefly. 



Meanwhile appeared in 1910 the publication of an investigation 

 of these equilibria at 25° by Ken.tiro Uyeda ^), to which our attention 

 was called by a communication thereon by E. Janecke "). His 

 figures agree very well with our determinations at 25°. Besides at 

 25°, we have determined the equilibrium also at 5', 50°, and 100°. 



We will indicate the composition of the solutions in the manner 

 proposed by E. Janecke ■') according to the scheme: 



,vK. (l-A-)iVa, ;/Nn,, (l ->/)CL mfl/)' 



in which m is, therefore, the number of grm. mols. of water in 

 which 1 grm. mol. of salt is dissolved. 



The graphic representation of the different solutions then becomes 

 a figure in space having as ground })lane a quadrangle of the 

 side =\ of which two sides coincide with the.?' and the ?/-axis. The 

 four salts then form the apexes of this quadrangle, mixtures of two 

 salts with homonymous ions are placed at the borders of this quadrangle 



1) Memoirs of the College of Science and Engineering, Kyoto Imperial University 

 1909/1910 II, 245—251. 



2) Zeitschr. f. anorg. Chem. 71, 1 (1911). 



s) Zeitschr f. anorg Chem. 51, 132 (1908); 71, 1 (1911). 



