----------+--------------+--------------+-------+------------ Type. | Dichromate. | Hydrochloric | Salt. | Aluminium | | Acid. | | Sulphate. ----------+--------------+--------------+-------+------------ | 5 | 2-1/2 | -- | -- | 5 | 2-1/2 | -- | 3 Schultz | 5 | 2-1/2 | 5 | -- | 5 | 2-1/2 | 10 | -- | 6 | 3 | -- | -- ----------+--------------+--------------+-------+------------ | 4 | 4 | -- | -- | 4 | 4 | 5 | -- | 5 | 5 | 5 | 3 Acid | 5 | 5 | 10 | -- | 6 | 6 | 15 | -- | 3 | 3 | 15 | 4 | 2 | 4 | 10 | -- | 4 | 15 | 24 | -- ----------+--------------+--------------+-------+------------ | 5 | 4-1/4 | 5 | -- | 5 | 4 | -- | 2-1/2 Neutral | Chromic acid | | | | 5 | -- | 5 | -- | 6 | -- | 8 | -- | 4 | -- | 10 | -- ----------+--------------+--------------+-------+------------ [Footnote 7: Commercial acids of course vary in strength, and the amount needed varies accordingly.]