October, '10] 



HINDS: FUMIGATION BOX MATERIALS 



397 



Most of the samples of duck used were obtained from Hettrick Bros., 

 Toledo, Ohio. In reference to the samples of brown waterproofed 

 ducks, Nos. 1, 2, 3, 8, 16 and 26, it appears that the Hghter weights 

 are fully as satisfactory in their gas-proof qualities and are less injured 

 by severe handling than are the heavy weights. The coating on this 

 material was but slightly soluble in liquid di-sulfid and would probably 



COMPARATIVE AIR POROSITY OF FUMIGATION MATERIALS 



Sample 

 No. 



10 

 11 



12 

 13 

 14 

 15 

 16 

 17 

 18 

 19 

 20 

 21 

 22 

 23 

 24 

 25 

 26 

 27 

 28 

 29 

 30 

 31 

 32 

 33 

 34 

 35 

 36 

 37 

 38 



Material and Treatment. 



7 oz. duck, Hettrick Bros., brown waterproofed 



8 oz. duck, _ " " " " 



10 oz. duck, " " " " " 



Good grade bond letter paper, coated with water glass 



Extra heavy ledger paper, tintreated 



Rubberoid roofing paper, two ply 



Light weight bond letter paper 



7 oz. waterproofed duck, severely crumpled and rubbed for one minute 



10 oz. duck, treated with one coat of glue containing some glycerine and water 



glass 



10 oz. duck, with one coat of glue with glycerine only 



10 oz. duck, with one coat of glue with some glycerine and one-half as much 



water glass 



Plaster of Paris, sheet 1-10 to 1-12 inch thick, dry 



Plaster of Paris, sheet 1-10 to 1-12 inch thick coated with vaseline 



10 oz. duck, with one coat of water glass, thinned with glycerine each side 



10 oz. duck, with two coats water glass, as above on one side 



8 oz. brown waterproofed duck severely rubbed one nainute 



20 oz. duck, untreated 



14 oz. duck, untreated 



10 oz. duck, with one coat water glass and no glycerine on one side 



10 oz. duck, with one coat water glass, thinned with glycerine on one side 



10 oz. duck, one coat water glass each side 



14 oz. paraffined duck 



18 oz. duck, untreated 



16 oz. paraffined duck 



16 oz. duck, untreated 



10 oz. brown waterproofed duck, severely rubbed 



Canoe duck, imtreated 



8 oz. army duck 



16 oz. paraffined duck, severely rubbed 



10 oz. duck, untreated 



Heavy gray felt, very spongy (weight 256) 



7 oz. army duck 



Thin cotton cloth, treated with " Preser\'o," (a waterproofing solution) 



Green felt, (piano-action felt) somewhat compressed 



Soft gray felt, (weight 285) 



Gray felt, (weight 181) 



Thin red felt 



Apparatus entirely open 



Percentage 

 of leakage. 



























1.8 



4.2 



7.1 

 9.5 



12.0 

 19.0 

 28.6 

 33.3 

 33.3 

 38.0 

 40.0 

 42.9 

 47.8 

 52.4 

 52.4 

 61.9 

 67.6 

 67.9 

 76.2 

 76.2 

 78.6 

 81.0 

 81.0 

 85.7 

 90.5 

 95.2 

 95.2 

 95.2 

 95.2 

 95.2 

 95.2 

 100.0 



prove resistant for a long time to the vapor. Paraffined duck samples 

 22, 24 and 29, while thoroughly water-proof, contained many com- 

 paratively large air holes, which place them all high in the percentage 

 of leakage. They were in fact even more porous than untreated 

 samples of the same weight. The addition of a small percentage of 

 glycerine in solutions of glue rendered the glue much less brittle, less 

 hable to cracking and slightly less porous than where glycerine was 

 omitted. The difficulty with all glue-coated samples seemed to be 

 that small airholes were formed in the coating, even on smooth sur- 

 faces, which opened when the glue dried and hardened, permitting the 

 passage of air even in cases where both sides of the cloth were treated. 

 It is noticeable that all the samples of felt are among the most 

 porous of the materials tested. In fact they have very little resistance 



