1821.] Action of Chlorides and Water. 31 



indeed this very decomposition on this principle must, I think, 

 prove fatal to what seems to be M. Gay-Lussac's opinion thai 

 chloride of sodium is not decomposed by water. If this latter 

 supposition be true, then, when sulphate of soda and muriate of 

 barytes suffer mutual decomposition, the muriate of soda which 

 is formed must exist as such only for a moment, and water must 

 be recomposed to form the chloride he supposes to exist. 



That the different temperatures which are occasioned by dis- 

 solving certain chlorides in water cannot, 1 think, be deemed a 

 criterion for determining the question may be inferred from a 

 very ingenious paper, contained in vol. xii. p. 42, of the Annales 

 de Chimie. In this memoir, upon the analysis of mixtures of 

 the chlorides of potassium and sodium, it is stated that under 

 similar circumstances a given weight of chloride of potassium 

 sinks Fahrenheit's thermometer 20-52°, and the same quantity 

 of chloride of sodium depresses it under the same circumstances 

 only 3*42°. Now it can, I think, hardly be supposed that bodies 

 so similar in their affinity for oxygen, as potassium and sodium, 

 should differ in their action on water when combined with chlo- 

 rine. We may consider these chlorides and that of barium as 

 converted into muriates by solution. 



With respect to the chloride of potassium and sodium, therie 

 are other reasons for believing them to be converted into mu- 

 riates by solution in water. In the first place, these metals have 

 strong afiinity for the oxygen of water, and so also has the 

 chlorine for its hydrogen, becoming muriatic acid when its 

 aqueous solution is exposed to the solar fight. As, however, 

 chlorine and these metals have also great affinity for each other, 

 it is certainly possible that this mutual affinity may diminish or 

 destroy their separate attraction for hydrogen and oxygen. It 

 must be granted, as before noticed, that whether we dissolve 

 dry chlorides in water, or saturate liquid muriatic acid with 

 metallic oxides, that similar solutions are produced. 



If to the solutions of chloride of sodium or potassium we add 

 sulphuric acid, their respective sulphates are formed, and a 

 similar effect, mutatis mutandis j is produced when tartaric acid 

 is used with the solution of potash. 



Now in these operations, one of two cases must occur. 

 Supposing we have dissolved potash in muriatic acid, and the 

 result to be solution of chloride of potassium, water must have 

 been formed, we then add tartaric acid, and this possesses the 

 power of so acting upon the elements of the solution that water 

 is again decomposed, and muriatic acid and potash again result, 

 as is evident by examining the solution and the crystaUine 

 deposit of the bitartrate of potash. 



The other case is simply this ; viz. that the chloride of potas- 

 sium immediately decomposes water, and then there is no ne- 

 cessity for attributing this power to the intervention of the sul- 

 phuric or tartaric acid. 



