i34 
The Australasian Scientific Magazine. [Xov. i, 1885. 
procedure is to dissolve 240 grammes of soda crystals (Na. 2 CO. . + 10 aq.) 
in one litre of water. This amount of alkali will be found sufficient for 
the strongest samples One litre of this alkaline solution will test ten 
samples of bleaching powder when 10 grammes are operated on, and 
twenty samples when 5 grammes are taken. I generally weigh out 5 
grammes of the samples of bleaching powder, then take 50 C.C. of the 
above alkaline solution, a little of which I add to the powder in a mortar, 
and triturate till there results a pasty mass; next the mortar is nearly 
filled with the alkaline solution, and the contents of the mortar rubbed up 
again with the pestle and transformed into a beaker. The remaining part 
of the alkaline solution is used for washing out the mortar into the beaker : 
water may be used to complete the washing if there be not enough of the 
alkaline solution. 
The contents of the beaker are allowed to settle for a few minutes, and 
the quickness with which they do so, is a measure of the good quality 
of the lime used in the manufacture of the bleaching powder. Bleachers 
much prefer the lime bleaching liquors (solution of bleaching powder), 
and alkaline bleaching liquors (the liquid I am now describing) which 
settles quickly. The supernatant liquid is then passed through a filter, 
and the precipitated carbonite of lime stirred up with some water and then 
thrown in the filter, the first portion of this film e should be received in a 
separate vessel as soon as the fine precipitate is liable to pass through, 
but some cease to do so ; when these portions can be filtered over again. 
The beaker and filter is then washed ; and the washings are known to be 
complete when they no longer give a precipitate with nitrate of silver or 
discharge the blue colour of the dilute solution of indigo. The latter test 
is the most convenient for bleachers, who generally use indigo for testing 
their bleaching vats for chlorine, and as the washing is easily effected, is 
sufficiently accurate. 
The filtered liquid to which the washings are first added is then made 
up with water to 500 C.C. It is easy to know when the liquid contains an 
excess of alkali, by the addition of a small portion of the lime bleaching 
liquid (sol. of bleaching powder), which if such be the case gives a white 
precipitate (carbonate oflime.) 
For each examination 50 cub. cent, of this liquid are taken, and the 
percentage of chlorine determined either by Gay-Lussac, or Penots’ 
method, with arsenious acid, or by Otto’s method with protoxide of iron or 
indeed by the usual methods. In the methods with arsenious acid, I find 
it a great improvement to dissolve the arsenious acid in glycerine instead 
of potassa or soda. If there is not time to filter, tolerably accurate results 
can be obtained by making up the unfiltered liquid to 500 cub. cent., 
indeed more accurate I consider than by the mere milky solution of the 
bleaching powder. 
Made up of this strength and filtered mere alkaline bleaching liquid is 
clear and colourless of a sp. gr. 1.007. I have made it, however, of a sp. 
gr. of 1.233 containing 1 of chlorine to 9 of the liquid, which in this case 
is slightly green. It has a pleasant oily feeling to the touch, contrasting 
favourably with the rough unpleasant feeling of the lime bleaching liquor" 
Its bleaching effect is very much altered by a slight departure on either 
side from its neutral point (viz., when the addition of either an alkaline or 
lime solution will cause no precipitate.) In the manufacture of this liquid 
for bleachers, the commercial carbonated soda ash is used with bleaching 
powder. 
