Within the last few years other forms of “antichlor” have been introduced, such, for example, as the various sulphites. The most important of these is sodium sulphite, which has been manufactured by a patent process at a cheap rate, by Gaskell, Deacon, & Co., Widnes. Their product contained as much as 75 per cent. of Na_{2}SO_{3}, ordinary crystallized sodium sulphite containing only 50 per cent. Sulphites are converted by the action of bleach into sulphates, thus:— Ca(OCl)_{2} + 2 Na_{2}SO_{3} = CaSO_{4} + 2 Na_{2}SO_{4} + 2 NaCl Calcium Sodium Calcium Sodium Sodium hypochlorite. sulphite. sulphate. sulphate. chloride. From this equation, it will be seen that 252 parts of sodium sulphite will neutralize 143 parts of calcium hypochlorite, or 204·3 parts of bleaching powder. Assuming that crystallized sodium sulphite contains 50 per cent. Na_{2}SO_{3}, the same amount of bleach would require 504 parts. As Messrs. Gaskell, Deacon & Co.’s sulphite contains 75 per cent. Na_{2}SO_{3}, only 336 parts are needed. Comparing these numbers with {129} those given above for sodium hyposulphite, it will be seen that 204·5 parts of bleach require for neutralisation 129 parts of sodium thiosulphate and 504 parts of crystallised sodium sulphite, or 336 parts of the stronger product. Sodium sulphite is preferred to sodium thiosulphate by some paper makers, notwithstanding the fact that even in its most concentrated form, nearly three times as much is required to produce a certain result. It is said that when it is used the wire cloth of the machine is preserved for a longer time than if sodium thiosulphate is employed. This may be due to the fact that with the latter a certain amount of free acid is always formed, which of course would act injuriously on the wire; whereas, when sodium sulphite is used, the products of decomposition are neutral salts without any action upon metals. (See the above equations.) A very cheap “antichlor” may be prepared by boiling together lime and sulphur. One hundred and sixty-eight parts of lime, made into a milk with water, are heated to boiling in an iron vessel. Three hundred and eighty-four parts of flour of sulphur or ground sulphur are then added in small quantities at a time, and the boiling continued until the whole is dissolved. The liquid which is now of a deep yellow colour, is allowed to settle and cool and is then ready for use. It contains a mixture of calcium thiosulphate and calcium pentasulphide, the latter compound giving to it its deep yellow colour. The following equation represents the action which takes place between the lime and the sulphur:— 3 CaO + 12 S = CaS_{2}O_{3} + 2 CaS_{5} Lime. Sulphur. Calcium Calcium thiosulphate. pentasulphide. The decomposition which takes place when the mixture is acted upon by calcium hypochlorite may be represented as follows:—