SOME TECHNICAL METHODS OF TESTING 

 MISCELLANEOUS SUPPLIES, 



Including Paints and Paint Materials, Inks, Lubricating Oils, Soaps, etc. 



INTRODUCTION. 



The Contracts Laboratory of the Bureau of Chemistry is called upon to ex- 

 amine a great variety of articles purchased by the Government. The character 

 of the examinations made varies to such an extent that it is not possible to 

 outline any general methods which are not subject to more or less variation 

 according to the purpose for which the material is intended. 



In this bulletin are assembled methods which have been found useful in a 

 large number of cases. As a general rule these methods, while not original, 

 have been compiled from a variety of sources and modifications introduced 

 when necessary. No attempt has been made, therefore, except in a few cases, 

 to refer to the original source. Acknowledgments, however, are due to the 

 following authorities: Lunge, Lewkowitsch, Rideal, Fernbach, Hall, Parry, 

 Hurst, Low, and many others. Nor has any attempt been made to give all of 

 the methods for the examination of any of the materials mentioned, but only 

 those which have been found most useful in this laboratory. 



The methods are presented in this form because of their inaccessibility at 

 present scattered as they are throughout chemical literature and because 

 those selected from the mass of material on the subject have been tested in 

 practice and found to be especially satisfactory. 



SPECIFIC GRAVITY DETERMINATIONS. 



1. Temperature Corrections. 



It is almost the universal custom among oil chemists in this country to 

 express the specific gravity of oils at 15.5 C. (60 F.) as compared with water 

 at the same temperature. Since this temperature is generally far below that 

 of the laboratory, the determination is frequently made at a higher tempera- 

 ture and the specific gravity calculated, using the formula G=G'+K 

 (T 15.5 C.), in which G=specific gravity at 15.5 C.; #'=speciflc gravity at 

 T, and K=meari correction for 1 C. 



The correction K varies somewhat for different oils, but the value "=0.00064 

 may be taken as sufficiently accurate in most cases for both hydrocarbon and 

 fatty oils. These corrections, however, only apply to specific gravities referred 

 to water at 15.5 C. (60 F.). The common custom of determining specific 

 gravity at higher temperatures compared with water at the same temperature 



For the value of K for different fatty oils see Allen's Commercial Organic 

 Analysis, third edition, 2 (1) : 33, and for lubricating oils see Archbutt and 

 Deeley, Lubrication and Lubricants, page 183. 



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