When the drying is complete remove the blocks from the drier, place them, while still warm, in the glass jars, with strips of blue litmus-paper between them and close the jars tight. They will then be stowed and inspected as dry gun-cotton. If the process of drying is not continuous the blocks must be kept in a powder tank, closed tight, when the drier is not in operation. DRYING BY EXPOSURE TO CALCIUM CHLORIDE (Ca Cl₂). This method requires:—5 lbs. calcium chloride (Ca Cl₂), 1 empty powder tank and 3 baking pans. The calcium chloride (Ca Cl₂) is cheap and can readily be obtained from any dealer in chemicals; it must not be confounded with chloride of lime or bleaching powder (CaO₂Cl₃). The latter has a strong odor of chlorine and, if used instead of the calcium chloride (Ca Cl₂), might cause decomposition of gun-cotton. The former is odorless and has no bleaching properties. To distinguish whether the substance has any bleaching properties, stir a small portion in an equal volume of water and immerse a piece of blue litmus-paper in the mixture. If the color disappears from the paper when dry (turning white), the substance is chloride of lime or bleaching powder (CaO₂Cl₂) and must not be used. The powder tank can be readily procured on board ship; care must be taken that it closes easily and air-tight. The baking pans should be of such a size that three of them will cover the bottom of the tank when placed alongside of each other; made of stout tin, free from solder, and 5 to 6 inches deep. Divide the calcium chloride between the three pans and place these pans, which must be clean and free from oil or grease, in the oven of the galley and allow them to remain there until all traces of moisture disappears. Stir the calcium chloride occasionally with a clean metal rod to expose the lower particles. Break it into pieces the size of a pigeon‘s egg. When all traces of moisture have disappeared remove the pans to a dry place and allow them to cool. The calcium chloride must not be put in the tank, nor the gun-cotton exposed to it, while warm. Place the tank in some suitable location where it will not be disturbed and, when the calcium chloride is cooled, place the pans in the bottom of the tank and lay over them a copper sieve, tinned copper wire being the best. Then place the blocks to be dried on the sieve and close the tank. Open the tank every 3 or 4 days, weigh the blocks, marking the weight and date with a soft lead-pencil on them and dry the calcium chloride as before. Continue this until the blocks have ceased to lose weight. While the calcium chloride is drying, the blocks are to be kept in the tank, which must be closed to exclude the moisture in the air. When they have ceased to lose weight stow them in the glass jars for dry gun-cotton primers, taking care to lay between them strips of blue litmus-paper, and treat them according to the rules laid down for dry gun-cotton.