86 THE AMEEICAN MONTHLY [April, 



pared, and are not used directly for staining, but are mixed with a cer- 

 tain amount of distilled or aniline water. In place of concentrated 

 watery solutions the alcoholic solutions can be used if five or six drops 

 are added to a small watch-glass of distilled water. This mixture is 

 often designated as the dilute alcoholic solution. From the watery or 

 alcoholic solution of the basic aniline colors the various staininsf fluids 

 are prepared. The preparations that are more commonly employed in 

 staining bacteria are Koch-Ehrlich's solution of methyl-violet or fuchsin, 

 and the alkaline methylene blue solution. 



A New Diatom Mounting Medium. 



By F. W. weir, 



NORWICH/ CONN. 



Cj()H^Br. -|- Resin of Tolu. — Dissolve 3 oz. of commercial bal- 

 sam tolu in 4 fl. drams of benzin (CgHg) at a temperature of about 

 45° C, and strain. Add 4 fl. oz. of carbon bi-sulphide, agitate thor- 

 oughly and allow to cool, when the tolu solution will separate and the 

 carbon bi-sulphide with cinnamic acid in solution can be decanted. 

 Add another portion of carbon bi-sulphide and treat as before. Fi- 

 nally pour the tolu solution into a glass tray and evaporate the benzin. 

 Place in a ^ oz. glass stoppered phial i fl. dram of naphthalin mono- 

 bromide and add gradually about three times its volume of the resin 

 of tolu, or sufiicient to make the mixture quite stifle when cold. The 

 solution will be effected slowly at about 45 '^ C. The above constitutes 

 a mounting medium which is rather easier to use than Canada balsam. 



Warm the medium at 40° to 45° C. until quite fluid, take up a mi- 

 nute quantity on a warm needle, place on centre of cover-glass and in- 

 vert on slide. Use no pressure whatever, but warm the slide gently, 

 when the medium will flow to the edge of cover. 



After a few days ring with a non-alcoholic cement. This method of 

 treating balsam tolu does not remove an atom of resin and does not 

 allow an atom of cinnamic acid to remain. The subsequent solution 

 in naphthalin-monobromide produces a medium of higher index (1.73) 

 than the resin alone, permanent in structure and volume, and free from 

 objections to which any medium in a volatile solvent is subject. 



Cleaning Diatoms. 



By J. J. MOLES, 



YARMOUTH, ENG. 



Having had a little experience in cleaning a large number of differ- 

 ent earths, I have found that each deposit requires a special treat- 

 ment ; but as a general rule, the following will prove useful : First 

 boil material in hydrochloric acid for two or three minutes in test-tube ; 

 allow to settle, pour off' the clear portion, and substitute nitric acid, of 

 course, both pure. Boil again for two or three minutes, then wash 

 well in distilled water in a tall beaker, allowing the sediment to settle ; 

 repeat the washing till all acid is removed. Now examine on slide. 

 Should the deposit not now be clean, boil with a small portion of soap ; 

 this removes a lot of " flock." Wash again to remove the soap ; then 

 decant, and add liquor ammonia (fort.) for 20 or 30 seconds. Lastly, 

 wash well in distilled water ; this leaves the pustules sharp and bril- 

 liant. — English Mechanic^ Dec. <5, i88g. 



