(4) The sizing and loading of paper: casein; gelatine; rosin size; alum; starch; silicate of soda; pigments and soluble dyes; mordants. Mineral substances for loading: clay, blanc fixe, etc. _Carbonate of Soda._--This substance, also known under the trade names of alkali and soda ash, is used in the paper mill for the manufacture of caustic soda. It is purchased by the paper-maker from the chemical works, and used together with the recovered ash (see page 78) for the production of caustic soda solution, which is required in the treatment of raw fibres. It is also used for the preparation of rosin size (see "Rosin Size") and in softening hard waters for steam-raising purposes. SODIUM CARBONATE TABLE. Showing percentage by weight and pounds per 100 gallons in solutions of various densities. ---------+-----------------------+----------------------------------- | Percentage by Weight. | 100 gallons contain pounds of Twaddell.+-----------------------+---------+-------------+----------- | Na_{2}O.|Na_{2}CO_{3}.| Na_{2}O.|Na_{2}CO_{3}.| 48 per | | | | |cent. Ash. ---------+---------+-------------+---------+-------------+----------- 1 | 0·28 | 0·47 | 2·76 | 4·72 | 5·74 2 | 0·56 | 0·95 | 5·61 | 9·60 | 11·68 3 | 0·84 | 1·42 | 8·42 | 14·41 | 17·56 4 | 1·11 | 1·90 | 11·34 | 19·38 | 23·64 5 | 1·39 | 2·38 | 14·26 | 24·40 | 29·73 6 | 1·67 | 2·85 | 17·10 | 29·36 | 35·77 7 | 1·95 | 3·33 | 20·16 | 34·46 | 42·00 8 | 2·22 | 3·80 | 23·12 | 39·52 | 48·15 9 | 2·50 | 4·28 | 26·17 | 44·72 | 54·50 10 | 2·78 | 4·76 | 29·71 | 50·00 | 60·90 11 | 3·06 | 5·23 | 32·27 | 55·18 | 67·22 12 | 3·34 | 5·71 | 35·36 | 60·50 | 73·72 13 | 3·61 | 6·17 | 38·43 | 65·72 | 80·07 14 | 3·88 | 6·64 | 41·57 | 71·06 | 86·58 15 | 4·16 | 7·10 | 44·65 | 76·33 | 93·03 16 | 4·42 | 7·57 | 47·80 | 81·77 | 99·61 17 | 4·70 | 8·04 | 51·02 | 87·24 | 106·31 18 | 4·97 | 8·51 | 54·25 | 92·74 | 113·10 19 | 5·24 | 8·97 | 57·45 | 98·26 | 119·70 20 | 5·52 | 9·43 | 60·67 | 103·70 | 126·42 21 | 5·79 | 9·90 | 63·98 | 109·40 | 133·45 22 | 6·06 | 10·37 | 67·32 | 115·10 | 140·12 23 | 6·33 | 10·83 | 70·63 | 120·81 | 147·10 24 | 6·61 | 11·30 | 74·00 | 126·62 | 154·20 25 | 6·88 | 11·76 | 77·38 | 132·30 | 161·12