Cases are named from their use or construc tion, as °Italic case," a two-third case for hold ing Italic type; °two-third case," a single case in which two-thirds of the space is equivalent to the ordinary lower case, and the remaining third is occupied by the capitals, etc.; °job case,* a single case suited to holding a small job font of type; °rule case," a case for holding brass rule; usort-case,* a case for containing °sorts.° The manufacture of cases has re ceived a serious set-back since the introduction of type-composing machines. See PRINTING.
the process of con verting the surface of certain kinds of mal leable-iron goods into steel, thereby making them harder, less liable to rust and capable of taking on a better polish. Fire-irons, gun locks, keys and other articles of limited size, are very.commonly so treated, but the process is sometimes applied to large objects, such as iron railway-bars. The articles are first formed, and heated to redness with powdered charcoal or cast-iron, the malleable iron taking carbon from either of these to form a skin of steel upon it; the heated objects are then cooled in cold water, or in oil when they are of a deli cate nature. Yellow prussiate or potash or
parings of leather have also been a good deal used for coating iron articles with steel by heating them together. Some chemists con sider that in this case nitrogen combines with the iron and effects the hardening. The coat ing of steel is very thin, seldom exceeding one sixteenth of an inch. Where a thicker coating is needed the articles are treated several times. The so-called °Harveyizing* process of harden ing steel armor plate is similar to case-harden ing in that the surface is made very resistant to the entrance of projectiles by heat treatment in carbon, while the back is softer and tough in order to resist the smashing effect of the projectile after it has penetrated the hardened surface. A Swedish ironmaster has found that a very excellent case-hardening is ob tained by treating iron or steel objects with a mixture of animal matter, such as rasped leather or horn, and arsenious acid dissolved in hydrochloric acid, and heating as usual. Charcoal alone is also used with success.