520 SCIENTIFIC RECORD FOR 1882. 



Constitution of Bleaching Powder. — Chemists have devoted much labor 

 to the determination of the exact constitution of bleaching powder, and 

 have arrived at results expressed in a great variety of formulae. 



Thorpe gives: CaaHgOgCli (= CaCl302+ CaCl^ + CaHgOz + 2H2O); 

 Eose gives : (CaCl2,Ca202) CaOzClz + 4 H2O; Kolb after a very thorough 

 investigation : (2 CaO C12H20), CaHaOz. Odling proposed the formula 



Cal^^ 



'^^ioci 



and this view has been quite generally adopted. Stahlschmidt regards 

 bleaching powder as calcium hydroxychloride, 



^^ i OCl, 



t. e.j calcium hydroxide, CaH202 in which one atom of hydrogen is 

 replaced by chlorine. 



The question has been again investigated by Dr. Karl Kraut, who 

 examined the action of chlorine on lithium hydroxide and obtained a 

 compound very similar to the calcium analogue. When chlorine gas 

 was brought in contact with the melted lithium hydroxide, the latter 

 increased only 1 per cent, in weight in 4^ hours, but by the addition of 

 crystallized lithia in such quantities that the mixture contained about 

 1.4 per cent. HgO the action of the chlorine was hastened. The reaction 

 is as follows : 



4 LiOH + 2 CI = LiCl + LiOCl + 2 LiOH + H2O 



This equation was confirmed by analysis of the product. The lithium 

 bleaching powder reacts with carbonic anliydride exactly like the cal- 

 cium compound, i. e., it is decomposed with liberation of chlorine. It 

 also behaves with chlorine just like the calcium compound. Since, how- 

 ever, lithium is a mono-valent element, one atom of the metal cannot 

 simultaneously bind chlorine and the radical of hypochlorous acid, and 

 Odling's manner of representing the constitution of bleaching powder 

 is inapplicable. Besides, the lithium bleaching powder contains lithium 

 chloride ready formed. The author therefore concludes that bleaching 

 powder is a mixture of calcium hypochlorite, calcium chloride, and cal- 

 cium hydrate. (Liebig's Annalen, ccxiv, p. 354.) 



Lead peroxide can be advantageously prepared, according to Fehr- 

 mann, by decomposing a concentrated solution of chloride of lead at 50° 

 or QO^ C. with a solution of bleaching powder. The latter is added un- 

 til the filtrate no longer shows a brown color when tested with an ad- 

 ditional quantity of the bleaching powder. The lead peroxide is well 

 "washed and collected on a filter. It is nearly black, and very pure. 

 The acetate of lead does not yield such good results as the chloride. 

 {Berichte d. chem. Ges., xv, p. 1882.) 



