1. Soya bean oil 120 2. Linseed oil 102 3. Calcium sulphate 93 4. Barytes 88 5. Asbestine 74 6. Corroded white lead 59 { Basic carb.--White lead 25% } { Basic sulph.--White lead 20% } 7. { Zinc oxide 25% } 58 { Calcium sulphate 25% } { Calcium carbonate 5% } 8. Sublimed white lead 56 9. Zinc oxide 56 { Zinc lead white 30% } 10. { Zinc oxide 40% } 42 { Basic carb.--White lead 20% } { Calcium carbonate 10% } 11. { Basic carb.--White lead 50% } 42 { Zinc oxide 50% } { Basic carb.--White lead 38% } 12. { Zinc oxide 48% } 38 { Silica 14% } The test boards were then exposed, with their content of water, to the action of the sun's rays. Blistering of the painted surfaces took place in many cases, caused by the rapid withdrawal of the water and its consequent action on the paint film. The tests seem to indicate that a mixture of white lead and zinc oxide, with or without a small percentage of the inert pigments, is not as subject to the action of the water as the single pigment paints. In order, however, to corroborate these tests, it occurred to the writer to develop a more visible means of demonstrating the passage of moisture through paint films. [Illustration: Bell Jar Apparatus for Testing Permeability of Paint Films Paint films sealed over mouths of Bottles containing Lime Water. Carbonic Acid Gas generated under Bell Jar passes through Plate Films and precipitates Calcium Carbonate] Another series of white pine boards were therefore soaked in a solution of iron sulphate for several hours. After removal, the surface of each board was dried and coated with one coat of the paints previously tested. After thorough drying for forty-eight hours, there was placed on the surface of each board a few drops of a solution of potassium ferrocyanide. This solution has the effect of producing a blue coloration with iron sulphate, and in every case when it was placed on a paint of considerable porosity, the solution penetrated through and formed a blue coloration beneath the paint. The results corroborated the original tests referred to above. A series of sheets or films of paints were then prepared according to the method referred to on page 71. These films were placed over glass dialyzing cups, allowing the inner surfaces to sag so as to hold a small amount of dilute ammonium chloride solution. Distilled water was placed on the reverse side of the dialyzing apparatus and the tests started. At the end of six days the distilled water in each test was examined and the following results obtained: