Mr. Crum o» Testing Solutions of Bleaching Powder. 



23 



of a degree. But if the liquor already in the vessel is found bj the 

 chlorimeter to produce a colour equal to the 2d phial, then 24 mea- 

 sures onlj are necessary, and so on. 



To stand -j^" 



requires 



1 -. 



2 — 



3 — 



4 — 



5 — 



6 — 



7 — 



32 

 28 

 24 

 20 

 16 

 12 

 8 

 4 



measures. 



To stand ^^ 



requires 16 measures. 



1 — 12 — 



2 — 8 — 



3 — 4 — 



To stand /g° 



requires 



2 — 



3 — 



4 — 



5 — 



24 

 20 

 16 

 12 

 8 

 4 



measures. 



To stand ^V 



requires 12 measures. 

 1^8 — 

 2 — 4 — 



Let us see what takes place on mixing chloride of lime with proto- 

 muriate of iron. On the old view of the constitution of bleaching 

 powder — that it is a combination of chlorine and lime, we have 



3 (CaO, Cl)> ^ . (I S^^l 

 6 FeCl i becommg < 2 Fe^Cla 



the peroxide of iron forming peracetate with the acetic acid which is 

 present Or, supposing with Balard that when two atoms of chlorine 

 unite with two atoms of lime, the product is CaCl + CaO, CIO, we 

 have this formula: 



3 CaCl ^ r 6 CaCl 



3 (CaO, CIO) V becoming \ 4 Fe^Cl, 

 12 FeCl J 12 Fe^Oa 



Here one third only of the iron goes to form the deep coloured per- 

 acetate, while the whole might be employed for that purpose, by using 

 protoacetate instead of protochloride. The latter however is preferred, 

 from the greater tendency of the acetate to attract oxygen from the 

 air, and consequently the greater difficulty of preserving it Even 

 with the chloride it is best to give out small quantities at a time, pre- 

 serving the stock in weU closed bottles. 



[Mr. Crum exhibited Dr. Clark's patent process for purifying water 

 from bicarbonate of lime.] 



