separately tested to determine solubility respectively in boric acid solutions and in sodium sulfate solutions at different concentrations the results are reported in table 5 table 5______________________________________solute filmg 100 cc water description______________________________________sodium sulfate 5 soluble 30 seconds 10 slimy 15 slimy 20 insoluble transparent film 30 insoluble transparent film boric acid1 soluble 2 minutes 3 stringy 5 insoluble turned white opaque in 2 minutes ______________________________________ from the foregoing tests it appears that while the soluble salts listed in table 4 above such as sodium sulfate can be employed to retard solubilization of polyvinyl alcohol films greater concentrations i e about 7 to 20 are required than when using boric acid as projected from the data set forth in tables 4and 5 potassium citrate appears to be even more efficient than sodium sulfate in the articles of this invention the specific behaviour of boric acid in retaining solubilization of pvoh film is not attributable to the ph of the boric acid solution whereas a vinol 205 film was insoluble in 5 boric acid solution such film was readily dissolved respectively in 5 aqueous solutions of citric and phosphoric acid and a 0 7 solution of fumaric acid the unexpected differences in the behaviour of borax versus.