984 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Cheap method of making' Absolute Alcohol.* — B. Sharp describes 

 a cheap method of making absolute alcohol, from the strong (95 per 

 cent.) spirit, used in Prof. Eanvier's laboratory in Paris. 



A wide-mouthed bottle is taken, holding about a litre, and three- 

 quarters filled with strong alcohol. A mass of pulverized cupric 

 sulphate (Cu SO4 + 5 Aq) is heated to a red heat in order to drive off 

 the water of crystallization. This is poured, when cool, into the 

 alcohol, the mouth of the bottle quickly closed, and the whole 

 shaken. The cupric sulphate is insoluble in alcohol, but has an 

 affinity for the water contained in it, and the water is consequently 

 taken uj), and the cupric sulphate becomes bluish. When this has 

 stood — with occasional shakings — for a day or so, decant, and repeat 

 the operation, especially if there is very much of a bluish colour in 

 the sediments. When finished a drop of alcohol can be mixed with a 

 drop of turpentine on an object-glass, and if there be no particles of 

 water to be seen under the Microscope, the alcohol is absolute enough 

 for all practical purposes. 



Arranging Sections and Diatoms in Series.f — P. Francotte has 

 modified the method of Dr. Van Heurck ("to render it more prac- 

 tical ") as follows : — 



(1) Dissolve (warm) from 7-10 gr. of glue in 100 gr. of water 

 (gelatin gives equally good results). A yellowish liquid is obtained 

 which becomes perfectly clear on cooling ; filter. 



(2) Spread this solution on the slide, in the same way as with 

 collodion or by means of a brush ; arrange the sections on the glass 

 while damp, and let it dry protected from the dust. To hasten 

 evaporation the preparation may be placed in a water-bath, or better 

 still, in an oven (at a temperature from 35° to 40" C). 



(3) When dry, warm gently over a lamp. The paraffin is re- 

 moved by tiu-pentine. 



(4) Apply the cover-glass coated with liquid balsam. 



The tui pontine should be washed with absolute alcohol, and then 

 the cover-glass coated with glycerin should be fixed if it is desired 

 to preserve the preparation in the latter reagent. If the object has 

 not been previously stained the sections can be very well stained 

 by a reagent which is dissolved in alcohol (hsematoxylin, eosin, anilin 

 dyes, &c.), alcohol not dissolving either glue or gelatin. It would 

 not be possible to use a staining agent in an aqueous solution 

 unless the sections were previously washed with tannic acid, which 

 would disadvantageously complicate the process. 



The method recommends itself to the author by the ease with 

 which the fixing liquid can be obtained ; the sections always adhere 

 perfectly ; no displacement is to be feared ; in washing, ether, chloro- 

 form, and oil of cloves can be used ; the mounting can be in balsam, 

 glycerin, or any other reagent. The wrinkles made in cutting are 

 effaced without difficulty. Sections obtained by imbedding in gum, 

 albumen, soap, or celloidin, can also be arranged by this method, but 



* Prnc. Acad. Nat. Sci. Philacl., 1884, p. 27. 

 t Bull. Sue. Beig. Micr., x. (1884) pp. 137-41. 



