(See also Adhesives, under Mucilages.)

Gums, their Solubility in Alcohol

The following table shows the great range of solubility of the various gums, and of various specimens of the same gum, in 60 per cent alcohol:

Acajon............. 6.94 to 42.92

Aden............... 0.60 to 26.90

Egyptian...........46.34

Yellow Amrad......26.90 to 32.16

White Amrad....... 0.54 to 1.50

Kordofan........... 1.40 to 6.06

Australian..........10.67 to 20.85-

Bombay............22.06 to 46.14

Cape............... 1.67 to 1.88

Embavi............25.92

Gedda............. 1.24 to 1.30

Ghatti.............31.60 to 70.32

Gheziereh.......... 1.50 to 12.16

Halebi............ 3.70 to 22.60

La Plata........... 9.65

Mogadore..........27.66

East Indian......... 3.24 to 74.84

Persian............. 1.74 to 17.34

Senegal............. 0.56 to 14.30

Substitute for Gum Arabic

Dissolve 250 parts of glue in 1,000 parts of boiling water and heat this glue solution on the water bath with a mixture of about 10 parts of barium peroxide of 75 per cent BaO2 and 5 parts of sulphuric acid (66°) mixed with 115 parts of water, for about 24 hours. After the time has elapsed, pour off from the barium sulphate, whereby a little sulphurous acid results owing to reduction of the sulphuric acid, which has a bleaching action and makes the glue somewhat paler. If this solution is mixed, with stirring, and dried upon glass plates in the drying-room, a product which can hardly be distinguished from gum arabic is obtained. An envelope sealed with this mucilage cannot be opened by moistening the envelope. The traces of free acid which it contains prevent the invasion of bacteria, hence all putrefaction. The adhesive power of the artificial gum is so enormous that the use of cork stoppers is quite excluded, since they crumble off every time the bottle is opened, so that finally a perfect wreath around the inner neck of the bottle is formed. Only metallic or porcelain stoppers should be used.