2338 



Journal of Applied Microscopy 



" The solution is stirred until all the soda has dissolved, and then filtered. 

 This bath should not be kept long, at all events when exposed to the carbon 

 dioxide of the air. When the exposure of a negative to such a solution has to be 

 prolonged, the solution itself should be changed about every half hour or forty 

 minutes. But when the action of the alkaline bath on the stain is slow, one may 

 as well use the acid bath, as prolonged exposure to the alkaline bath causes the 

 image to be very considerably, if not entirely, chlorinated. The action goes on 

 to a greater extent when the amount of alkali in the bath is lessened, as happens 

 when carbonic acid is absorbed from the air. The advantages of the acid bath, 

 when we cannot help chlorination, are that it does not apparently harm the film, 

 and it is rather more powerful in its bleaching properties. 



" It is a most unfortunate fact that these alkaline hypochlorite and hypo- 

 bromite solutions affect the gelatine film most objectionably, causing frilling of 

 an extreme character, and if too strong, dissolving it together. The solution 

 above given has these faults, I believe, in a minimum degree. 



" Alkaline hypochlorite and hypobromite solutions have a pleasant seaweed 

 like smell. This is due to free hypobromous or hypochlorous acid, which is 

 formed by hydrolysis even in the presence of large excess of alkali, and is 

 really the active part of the solution. 



" Summing up, I may say I believe that all developer stains can be bleached 

 out by the use of an acid or alkaline bleaching powder solution, although it may 

 not always be possible entirely to prevent the recrudescence of the trouble when 

 the negative has to be reblackened, owing to the image having been chlorinated." 



A Microscopical Reagent Bottle. 



The accompanying sketch shows a form of dropping bottle for containing 

 and applying microscopical stains and reagents, which has been found useful in 

 histological work. It is easily fitted up, if a small wide-mouthed bottle provided 

 with a tight-fitting cork be procured. A couple of small 

 pieces of glass tubing, an india-rubber bulb, and a tiny piece 

 of india-rubber tubing to connect up the outlet tube will 

 complete the arrangement. Briefly, its advantages consist 

 in keeping the reagent free from contamination with dust, 

 and allowing of its removal without taking out a stopper or 

 cork. In addition, complete control over the amount of re- 

 agent deposited on a slide is obtained by varying the hand- 

 pressure on the bulb. An empty bottle of this description 

 can also be utilized to remove excess of liquid from a slide, 

 by pressing the bulb tightly, inserting the outlet tube in the 

 liquid, and then gradually removing the pressure on bulb, when of course the 

 liquid will be forced up the tube by atmospheric pressure, as with an ordinary 

 syringe. A wide-mouthed test tube, if fitted up like this, will be found useful in 

 picking out the larger forms of pond life from a large gathering, by using it in a 

 similar way to a pipette. — Eng. Mcch. and Eng., No. 1984. 



