1896.] BypocMorites to GJdorates. 71 



The preparation of hypochlorites in a weighable state, so that the 

 available chlorine can be calculated, is almost impossible. Kingzett 

 obtained crystals of very nearly pure calcium hypochlorite {Journ. Chem. 

 Soc, [2]. 13, 404) containing an unknown number of molecules of water. 

 The greatest precautions as to increase of temperature, contact with dust 

 and exposure to actinic rays, can not prevent decomposition when 

 hypochlorites are evaporated in vacuo over sulphuric acid. No direct 

 evidence can therefore be adduced to test one method or the other. 

 Concordance of results as obtained by different methods is the only test. 



It has already been stated that phosphoric acid failed to decompose 

 chlorates. Similar experiments were performed with the result that the 

 whole of the hypochloroiis acid was carried along with carbon dioxide into 

 the absorption apparatus, and liberated iodine from potassium iodide. 

 The residue (when chlorate was likewise present) when distilled with 

 pure hydrochloric acid gave the chlorine of the chlorate. Direct estim. 

 ation of chlorate and hypochlorite in a mixture containing the same is 

 thus rendered possible and practicable. 



Hypochlorites can also be estimated by the action of potassium 

 iodide in acid (HCl or Hg PO4) solution. 



To test whether any free oxygen is liberated from the decomposi- 

 tion of hypochlorous acid, the apparatus, as given in the annexed 

 diagram (Plate III) was used. 



The distilling bulb, parts of which were all fitted by grinding, 

 contained water and pieces of marble or calcite (freed from air by boil- 

 ing with water) introduced through A. Through B, a solution of 

 potassium iodide was introduced in C, so that the level was slightly 

 below the open end of the tube C. The U tube contained a more 

 dilute solution of the same. Air from the apparatus was expelled by 

 passing carbon dioxide though D, and when the bubbles were perfectly 

 absorbed by potash solution contained in the gas measuring tube in the 

 mercurial trough, the stop cock S was closed, and the solution of hypo- 

 chlorite introduced in the bulb E. As the pressure inside the apparatus 

 was greater than the atmospheric pressure, the solution was introduced 

 by a very careful blowing, and then the sides carefully washed down. 

 Pure syrupy phosphoric acid was similarly introduced, the stop cock S 

 closed, and the bulb slowly heated to boiling on an asbestos board. 

 The hypochlorous acid along with the carbon dioxide generated inside the 

 apparatus passed through the solution. Iodine was thus liberated. 

 Evolution of carbon dioxide was kept steady, but even after an hour 

 no oxygen was found in the measuring tube. Hence no loss of chlorine 

 takes place when hypochlorous acid is distilled with phosphoric acid 

 in dilute solution. 



