CHAPTER XI 

 ADDITIONAL TESTS AT ATLANTIC CITY AND PITTSBURG 



A SERIES of new test panels to take the place of those panels 

 which were condemned and subsequently removed from the 

 Atlantic City and Pittsburg fences, were painted and exposed 

 during June, 1909. These new test panels are of white pine, 

 this wood having been selected by the joint inspection com- 

 mittee as offering the best condition for future tests. The 

 method used in painting these panels was the same as in the 

 previous tests, together with the adoption of certain refinements 

 in the reductions, application, etc. Thirty-six formulas were 

 selected with careful regard to the percentage of components, 

 including several paints containing lithopone combined with 

 whiting and zinc oxide, 1 two pigments which gave promise of 

 supporting the lithopone for outside use. Some of these litho- 

 pone paints contained special vehicles which it was thought 

 would prevent the destructive action which lithopone seems to 

 have upon linseed oil. In order to obtain a criterion of the 

 value of the new formulas applied, as against the wearing of 



1 A brief study of the theory of solutions (See Cushman and Gardner on 

 "Corrosion and Preservation of Iron and Steel"), involving the modes of 

 iron formation, will be invaluable to the student who is inquiring into the 

 cause of the peculiar fogging of lithopone, with the idea in view of correcting 

 this evil by physical or chemical treatment. Inasmuch as our observations 

 thus far have led us to believe that the fogging of lithopone takes place in the 

 presence of moisture, with the contributory and necessary action of chemi- 

 cally active rays from the sun or other source, it is fair to assume that under 

 these conditions the insoluble molecule of zinc sulphide and barium sulphate 

 reverts by intricate molecular disturbance and ionization back to the soluble 

 barium sulphide and zinc sulphate from which the lithopone is formed by 

 metathesis. If this be true, then the acid nature of these soluble salts is no 

 doubt combated and overcome at the moment of formation by the basic 

 nature of zinc oxide and calcium carbonate, which tend to ionize to an 

 alkaline reaction. The value of zinc oxide and calcium carbonate in litho- 

 pone paints as detergents of blackness, has been demonstrated at both 

 Atlantic City and Pittsburg." H. A. G. 



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