PHYSICAL LABORATORY PAINT TESTS 



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paints in which they are ground. Lead and zinc paints, of 

 course, have the greatest drying values on account of the added 

 effect of the linoleates formed, as outlined above. The writer 

 has made a series of tests in which the action of various pigments 

 upon linseed oil is shown. The tests were made in the following 

 manner: 



Five grams of each of a series of commonly used paint pigments, 

 including those of inert crystalline nature as well as the more 

 valuable amorphous pigments which are considered more or 

 less chemically active, were ground separately in an agate 

 mortar, with 5 grams of raw linseed oil. The ground paste 

 in each case was placed in a marked glass beaker, and allowed 

 to stand in a dustless section of the laboratory for one month. 

 The oil-pigment paste from each beaker was then separately 

 extracted with benzine to remove the linseed oil from the pig- 

 ment. The benzine solutions of oil were then heated to remove 

 the benzine and the residue of oil burned to ash in crucibles. 

 The ash from each test was weighed, and if it ran above the 

 percentage of ash determined on a blank sample of linseed oil 

 (namely, .003%), the ash was analyzed qualitatively for metallic 

 constituents. The following table of results shows the per- 

 centage increase in ash, as well as the constituents of ash on the 

 various samples tested: 



TABLE OF RESULTS 



