1889.] MICROSCOPICAL JOURNAL. 127 



Carbolic Acid in Mounting.* 



By F. T. CHAPMAN. 



Phenol, carbolic acid, coal tar, creosote, phenic acid, and phenylic 

 alcohol are various names, according to Ure, for a substance more com- 

 monly known by the second name, carbolic acid. At ordinary tem- 

 peratures, according to the same authority, it crystallized in long color- 

 less needles, which easily deliquesce to an oil taking up a mere trace 

 of water, but which may be made to immediately solidify by the addi- 

 tion of chloride of lime. It dissolves sparingly in water but well in 

 alcohol, ether, and strong acetic acid. 



I became interested in the use of carbolic acid for preparing insects 

 for mounting, as the usual methods were open to objection. With liq. 

 potassa, none but the harder, chitinous parts remained, and the 

 " skeleton" was usually distorted by being mashed. Turpentine is a 

 good clearing agent, but takes too long a time to act, being, however, 

 in most other respects unobjectionable. 



According to all the information I could gather ; the strongest un- 

 colored acid must be used, and small insects could be cleaned in a few 

 seconds, and immediately mounted in balsam without further treatment. 



To liquefy the crystallized acid I find that the addition of a few drops 

 of water is amply sufficient, say about 5 or 10 drops to the ounce of 

 acid. Or if it can be used warm, and its action is hastened by heat, it 

 may be temporarily liquefied at a comparatively low temperature, and 

 does not again solidify until quite cold. No set time for treatment of 

 the insect can be given, as it will vary from a few minutes to several 

 days. For instance, the head of the common house fly, which is an 

 unusually difficult object to clear, takes about a week, but well repays 

 one for the labor when finished. 



I have not succeeded in any instance in mounting an object in ben- 

 zole balsam directly from the acid, as a permanent, opaque cloudiness 

 invariably appeared, whether the acid was liquefied by water or 95% 

 alcohol. To prevent this clouding, which was probably due to the 

 presence of water in the carbolic acid, the object was first passed through 

 clove oil, that is, the object was allowed to remain in the oil until all 

 surface agitation disappeared, and Was then mounted in benzole balsam 

 in the usual manner. 



It may be well to mention that the object is mounted without pressure, 

 in a cell of suitable depth, and that flattening, and consequently distort- 

 ing, the object is to be condemned, as it is then misleading and does 

 not present its well rounded and beautiful natural proportions. When 

 strong carbolic acid is used to clear insects it causes all the exterior 

 retractile organs to protrude as they do naturally. 



It was suggested in the Microscope for January, 1889, that the ana- 

 line dies could be dissolved in creosote, and the object stained as well 

 as cleared. Although creasote (C 13 H lt! O 3 ) differs from carbolic 

 acid (O H 6 O) when both are pure, it is quite probable that the latter 

 will prove a good vehicle for stains. The analines will probably dis- 

 solve freely, as will also picric acid and carmine, and double staining 

 can likely be successfully performed. The strength of the stains will 

 have to be graded according to the object, or it may be cleared and then 



* Read at the Washington Mic. Soc. 87th Regular Meeting, Feby. 12, 1889. 



