192 



THE AMERICAN MONTHLY 



[October, 



Etliyl-^ther of Gallic Acid, and 

 a New Mouutiiig Material. 



BY PROF. CHRISTOPHER JOHNSTON, M.D. 



In the month of November, 1882, 

 my young friend, Dr. R. Dorsey Coole, 

 of the Johns Hopkins University, 

 kindly gave me a little vial, containing 

 a pale buff powder composed of mi- 

 nute acicular crystals, and labelled 

 Ethyl-^ther of Gallic Acid. And he 

 added to the favor by furnishing me 

 with the formula indicating its consti- 

 tution, as thus : C ' H -^ (O Hj ^ CO 



I found this substance to be most 

 readily soluble in water, alcohol and 

 aether, and to crystallize out on the 

 slide in masses of irregular rhombic 

 form, in needles, in elongated prisms, 

 and in discs of many sizes, and, ac- 

 cording to thinness, of various colors, 

 beginning with the steel gray, passing 

 through blue-gray, and ending in hues 

 as vivid as it is possible to conceive. 

 The smaller crystals, however, were 



in the majority, and greatly marred 

 the beauty of the preparations. 



But I was doomed to disappoint- 

 ment in discovering that the film of 

 splendid, glowing forms, discs and 

 rosettes, sooner or later began to fade, 

 and, in most instances, dissolved, and 

 like the baseless fabric of a vision left 

 not a rack behind. The dimmed brill- 

 iancy of a few slides, however, at- 

 tested the beauty of the object, and 

 one of these attracted attention at the 

 last public exhibition of the Baltimore 

 Microscopical Society, held in the 

 spring of the present year. After 

 that meeting I resolved to test some 

 better modes of preparing the crys- 

 tals ; and, what was indispensible, to 

 find a mounting material — for they 

 must be embalmed, and will not en- 

 dure the air — which should preserve 

 and not extinguish the film. I there- 

 fore instituted the following experi- 

 ments in mounting crystals of ethyl- 

 aether of gallic acid, coming out of 

 solution in absolute alcohol. 



MATERIAL. 



1. Pure, soft Canada Balsam. 



2. Old Canada Balsam in Chloroform. 



3. Old inspissated Chian Turpentine with 



common Turpentine. 



4. Old hard Damar in Turpentine (dried 



out of a Benzole solution). 



5. Damar and Mastic in Benzole. 



6. Boiled Linseed oil and No. 3. 



7. Copal Varnish (Coach). 



8. Castor oil. 



9. Best Piano Copal Varnish. 

 ID. Oil of Amber. 



After these failures I sought new combin 



11. A drop of Petrolina oil upon the slide, 



followed by a drop of No. 3. 



12. Balsam Copaiba. 



13. Boiled Balsam Copaiba. 



14. Boiled Copaiba and old Chian Turpen- 



tine. 



15. First a drop of boiled Copaiba, then old 



Chian Turpentine dissolved by boil- 

 ing in Balsam Copaiba. 



16. Boiled Balsam Copaiba thickened de- 



cidedly with clear Virgin Rosin of a 

 pale straw color. 



Dissolved the crystals. 



Dissolved much, especially the 

 thinner gray rosettes. 



Dissolved nearly everything. 



Dissolved everything, or at least 



destroyed. 

 Dissolved. 

 Dissolved. 

 Dissolved. 



Dissolved finer parts. 

 Dissolved. 



ations, thus : 

 Partial success. 



Quite good. 

 Very good. 



Very excellent — but the ghostly 

 crystalline plates vanish slowly. 



The best success, but not perfectly 

 satisfactory. 



Preserves everything unless it be 

 the dark-looking rhombs which 

 ^ield if proceeding from certain 

 solutions. Even salicylate .of 

 Cinchonidia remained about 

 firm. 



