The Poisons and Pharmacy Act of 1908 extended the schedule of poisons instituted by the act of 1868, and it now includes arsenic, aconite, aconitine and their preparations; all poisonous vegetable alkaloids, and their salts and poisonous derivatives; atropine and its salts and their preparations; belladonna and all preparations or admixtures (except belladonna plasters) containing 0.1% or more of belladonna alkaloid; cantharides and its poisonous derivatives; any preparation or admixture of coca-leaves containing 0.1% or more of coca alkaloids; corrosive sublimate; cyanide of potassium and all poisonous cyanides and their preparations; tartar emetic, nux vomica, and all preparations or admixtures containing 0.2% or more of strychnine; opium and all preparations and admixtures containing 1% or more of morphine; picro-toxine; prussic acid and all preparations and admixtures containing o i% or more of prussic acid; savin and its oil, and all preparations or admixtures containing savin or its oil.
Thus its non-liability to freeze (when not absolutely anhydrous, which it practically never is when freely exposed to the air) and its nonvolatility at ordinary temperatures, combined with its power of always keeping fluid and not drying up and hardening, render it valuable as a lubricating agent for clockwork, watches, &c., as a substitute for water in wet gas-meters, and as an ingredient in cataplasms, plasters, modelling clay, pasty colouring matters, dyeing materials, moist colours for artists, and numerous other analogous substances which are required to be kept in a permanently soft condition.
In a scientific definition the compounds of fatty acids with basic metallic oxides, lime, magnesia, lead oxide, &c., should also be included under soap; but, as these compounds are insoluble in water, while the very essence of a soap in its industrial relations is solubility, it is better to speak of the insoluble compounds as " plasters, " limiting the name " soap " as the compounds of fatty acids with soda and potash.
They form excellent decorative plasters on account of their clean white colour and the sharpness of castings made from them, this latter quantity being due to their expansion when setting.
C. Eckel, Cements, Limes and Plasters (New York, 190s); G.
How would you define plasters? Add your definition here.