Generally speaking, the sulphuretted hydrogen and sodium sulphite methods are to be preferred.

Because of this reaction sodium sulphite is used as a convenient source of sulphur dioxide.

The sodium sulphite method has the advantages of being clean and neat, and of requiring no nitration.

The jute acetate showed the normal reaction with chlorine, and the lignone chloride was dissolved by treatment with sodium sulphite solution.

In addition, if an excess of sodium sulphite has been used and enough acid not subsequently added, the excess will count as iron.

Moreover, an investigation of the products dissolved by sodium sulphite solution from the chlorinated fibre has shown that they are practically free from furfuroids.