Notwithstanding all the attempts that have been made, the use of a lead-lined boiler is a serious objection, and any process which will fulfil the conditions on which the bi-sulphite processes depend, and which at the same time admits of the use of the ordinary iron boilers, is an obvious desideratum. Such a process is that patented by one of the authors (Cross, No. 4984, 1880), claiming the use of solutions of the neutral sulphites with or without the further addition of an alkali. This process is very suitable for the treatment of fibres such as straw, jute, &c., but not economically applicable to the preparation of wood pulp on account of the cost of chemicals. The preservative effect of the sulphite is shown by the largely increased yield of pulp. The chief advantages of the various bi-sulphite processes for the preparation of wood pulp over the old soda processes are, (1) the increased yield of fibre; (2) the preservation of its original strength, and (3), the economy in chemicals. It is well known that cellulose, even in its most stable forms, is attacked more or less by hot solutions of the caustic alkalis, and is more or less profoundly modified according to the strength of the solution and the temperature at which it is employed; while on the other hand the solutions of the bisulphites affect it but little. Thus, the authors have exposed jute cellulose, which is of the same nature as that obtained from wood, to the action of magnesium bisulphite under the conditions which obtain in the Ekman process, without its undergoing sensible loss of weight, and further, they have determined the amount of cellulose in freshly cut grasses, in which it is but imperfectly elaborated, and therefore very susceptible of modification, both before and after treatment by the process, and in each case the percentage obtained was the same. There is therefore no doubt that in the bisulphite processes, even the structurally delicate forms of cellulose are conserved. As before indicated, the influence of this upon the yield of cellulose is of course very marked; the yield from white pine, {77} by the soda process, being approximately 33 per cent., whereas by the Ekman process it is from 45–50 per cent. It is important to remember that this increased yield of cellulose cannot fail to affect the quality, and therefore the paper-making properties of the pulp. Papers made entirely by the bisulphite processes have a strongly marked individuality, being distinguished by their hardness and transparency. In regard to the bleaching of the pulp, it will be found that some practical experience is required for the control of the operation, so as to produce uniform results.