Q.: Item 26 in the March 1977 issue, page 132, talked about removing oil stains from concrete. It advocated using 1 pound trisodium phosphate per gallon of water and mixed with whiting to make a paste. Did you mean anhydrous trisodium phosphate or crystalline trisodium phosphate? We mixed crystalline material with water and it just sits on the bottom of the barrel and doesn't dissolve. We don't have any way of heating the water on the job.
A.: Our source didn't say whether the trisodium phosphate (TSP) should be anhydrous or a crystalline hydrate. The anhydrous material would make a more concentrated paste, but as a practical matter either one should work. Actually, either one is more soluble. even at 50°F. than the l-pound-per-gallon recommendation, though it might take a lot of mixing before dissolving is complete. If there is no way of heating water on the job the solution could be made up elsewhere and trucked to the site.