Issued August 10, 1911. 



United States Department of Agriculture. 



BUREAU OF CHEMISTRY Circular No. 77. 

 H. W. WILEY, Chief of Bureau. 



THE DETERMINATION OF CAMPHOR. 



H. C. Fuller, Assistant Chemist, Division of Drugs. 



The extensive use of camphor in medicine and the fact that the 

 Pharmacopoeia includes preparations which must contain definite quan- 

 tities of camphor make it imperative that there should be a reliable 

 method of assay. There have been in vogue for some time procedures 

 depending on the rotation of an alcoholic, benzol, or oil solution and 

 on the loss by evaporation, but they are open to objection, and in cer- 

 tain instances the results might easily be misinterpreted. Artificial 

 camphor is without rotatory power, natural camphor might contain a 

 portion of the levo body, the rotation varies with the strength of the 

 solvent, and fixed oils themselves on heating often undergo loss or 

 gain in weight. These are a few of the reasons which call for a method 

 based on a more substantial foundation. 



Camphor, being of ketonic character, forms with hydroxylamin a 

 well defined oxim C 10 H 16 NOH, and advantage has been taken of this 

 property in assaying camphor preparations, the procedure being based 

 on Walther's l carvone estimation and on the work of Nelson, 2 who 

 determined in essential oils by the hydroxylamin method a number of 

 ketones including camphor. The procedure is simple and may ^ 

 applied directly to spirits of camphor. Of the sample 25 cc arejl c 

 measured into an Erlenmeyer flask of 100 cc capacity, 2 grams of 

 sodium bicarbonate are added, and then, accurately, from a burette, 

 35 cc of a hydroxylamin solution (20 grams NH 2 OH.HC1 + 30 cc 

 H 2 O + 125 cc absolute alcohol aldehyde free). The flask is connected 

 with a reflux condenser, and heated to gentle boiling for two hours; 

 it is then cooled to 25 C., treated with a mixture of 6 cc hydrochloric 

 acid (1.12 specific gravity + 6 cc water) transferred to a 500 cc volu- 

 metric flask, rinsing out the condenser and flask with water, and finally 

 made up to volume; 50 cc portions are filtered off and titrated as 

 follows: Methyl orange is added and the mineral acid neutralized with 

 normal alkali, then phenolphthalein is added and the hydroxylamin 

 hydrochlorid titrated with tenth-normal alkali. A blank must be run 

 using the same amount of hydroxylamin solution and 25 cc of alcohol 

 to correspond with the spirits of camphor, the difference in titrations 

 representing the hydroxylamin converted into camphor oxim. Each 

 cubic centimeter of tenth-normal sodium hydroxid is equivalent to 

 0.01509 gram of camphor. 



i Pharm. Centralhalle, 1900, 41: 613. 2 U. S. Dept. Agr., Bureau of Chemistry Bui. 137, p. 186. 



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