854 



EECOKD OF CUKRENT RESEARCHES RELATING TO 



to staining, avoiding the inconvenience of alcohol which is very 

 slow in action and not always certain in result, and solutions of 

 lime chloride and chlorinated soda (Labarraque's) which so disinte- 

 grate that many delicate tissues are utterly ruined. The former 

 solution, in addition to its direct destructive influence, has a great 

 tendency to permit of the formation on its surface of a scum of 

 carbonate of lime ; this, sinking into the fluid, settles itself upon the 

 sections, so that if they escape absolute destruction they are in 

 danger of becoming coated with a brittle film, which proves equally 

 ruinous to them. 



The apparatus employed for the purpose is shown in Fig. 80, and 

 consists of two small wide-necked (1 oz.) bottles, with a bent glass 

 (quill) tube passing through the centre of sound and accurately 

 fitting corks which are made air-tight by shellac varnish. A notch 

 is cut in the edge of the cork carrying the longer arm of the tube. 



Fig. 80. 



Fig. 81. 



To use the apparatus, fill the bottle A three parts full with filtered 

 rain-water, and to this transfer the sections to be bleached. Into 

 bottle B put a suificient quantity of crystals of chlorate of potash just 

 to cover the bottom, and upon them pour a drachm or so of strong 

 hydrochloric acid, and fit in the corks. Immediately the yellow 

 vapour of chlorine (or, strictly speaking, of euchlorine) will be ob- 

 served to fill the bottle B, whence it will pass along the connecting 

 tube into the water contained in the bottle A, and effectually and 

 safely bleach the sections. When the water becomes supersaturated, 

 the excess of chlorine will accumulate in the bottle above the liquid, 

 and find an exit through the notch in the cork. As to the time 

 required for bleaching, this of coiarse will vary in accordance with the 

 nature of the sections operated upon. If the apparatus is set to work 

 at night (out of doors, in a covered place), in the morning the bleach- 

 ing is generally found to be complete ; if not, further time may be 

 allowed, without any danger to the sections being incurred. 



Decoloration having been effected, the sections must be thoroughly 

 washed to eliminate all trace of chlorine before employing any stain - 

 ing agent. The usual method of effecting this is to put the sections 

 into a large basin full of water, and repeatedly to change the water. 

 As this process is not only tedious, but exposes the sections to consider- 



