Chemical Science. 485 



so that the only change necessary will be to use ten times as 

 much of the solution of chlorine to be tried, as was taken upon 

 the former system, whilst the strength of the solution will be 

 estimated in the same degree as before. 



' When muriate of manganese is poured into solution of chloride 

 pf lime, the muriatic acid takes the lime, brown oxide of man- 

 ganese is precipitated, and the chlorine disengaged. The quan- 

 tity of liquid decomposed corresponds exactly to that of the 

 chlorine disengaged. In this case the disengagement of the gas is 

 the result of a reaction, and the latter may be effected either very 

 slowly, or in an interrupted manner, without any sensible differ- 

 ence in the estimation. The liquid will keep for many months 

 without change ; but as at length a small brown deposite is formed, 

 it is well to add 10 drops of muriatic acid to each litre (61 cubic 

 inches) of the proof liquor. Supposing the substance will not keep 

 indefinitely, still it may be remarked, that a diminution in strength 

 is of much less consequence than variations in trials made at the 

 same time. The value of the liquor is at any time readily ascer- 

 tained, or its strength corrected. 



M. Morin's memoir contains a long series of experiments upon 

 the effects produced by variations in the proportion of water, by 

 heat, air, time, upon the substance. His results are not in ac- 

 cordance with Dr. Ure's, but agree with M. Welter's. 



The hydrate of lime, consisting of 2 proportions of water, and 

 2 of lime, is that which absorbs the largest quantity of chlorine. 

 If otherwise constituted, the chlorine is proportional to the body 

 in smallest quantity ; and, in such cases, the excess of lime, or of 

 water, is a pure loss in the chloride. Two proportions of quick lime 

 dipped into water, and taken out, contain about 2 proportions of 

 water; but, after being allowed to slake, they retain little more 

 than one proportion of water. The manufacturer should be careful 

 to add a quantity of water equal to that which has evaporated: 

 a little excess is much better than having an excess of lime. 



When bleaching powder is prepared, the temperature should be 

 kept low : when made quite cold, it always marked full strength 

 or 100° upon the chlorometer, all the chlorine being then in an 

 effective state as chloride of lime ; but when the heat was allowed 

 to rise, the chloride sunk in value to 66°, so that one-third of the 

 chlorine was lost, and that was the case whatever the temperature 

 was between 30° and U9° (86° and 246° Fah.): no oxygen was dis- 

 engaged, but chloride of calcium and chlorate of lime formed at 

 such times. In all these experiments, 2 proportions of hydrate 

 absorbed 1 proportion of chlorine. 



When the chloride of lime in powder is carefully heated, a con- 

 siderable quantity of chlorine is given off at first, and then oxygen. 

 If the sohition be heated, pure oxygen is evolved, and by ebullition 

 all the chloride of lime is destroyed. 

 The following appears to be the composition and condition of 



