localities where there are deposits of iron pyrites) into the autoclave. The sulphur dioxide gas, under pressure, penetrates the pores of the wood, and uniting with the moisture there forms sulphurous acid, which serves the purpose of the more expensive sulphuric acid in Simonsen's process. When the autoclave is opened the excess of sulphurous acid gas is easily driven off and may be used on a fresh portion of wood. Furthermore, as less acid is left, less lime is required for the neutralization which must precede the fermentation. The claim is made that 25 gallons of absolute alcohol have been made from one long ton of sawdust by Classen's process.
Numerous modifications have been suggested, tried and patented, but this is not the place to enter upon a detailed account of these refinements. Perhaps the most interesting is the claim made by Gentzen and Roth in their patent that the addition of ozone, while the wood is being acted upon by acids and is under pressure, materially increases the amount of cellulose converted into dextrose, glucose and fermentable sugars.
The methods may be said to be on the verge of financial success and some small change or addition may any day convert a moderately profitable process into a brilliant success. Problems for physical chemists abound in these processes. We need to know exactly the most favorable concentration of acid, the best temperatures and pressures to be applied and the proper length of time during which the acid, heat and pressure should be allowed to act. Some work has been done on these questions and more is being done. For instance, it has been proved that prolonged action of the acid is harmful, for fermentable sugars which are formed early are later destroyed. It is therefore necessary to interrupt the process at the right time. Such experiments cost money and the time of highly educated men, and no one would dare to say positively that they would result in the discovery of a bonanza. Unfortunately, our manufacturers do not yet realize of what value truly scientific, highly trained, high-priced men would be to them, while the German manufacturers do, and so we may expect these, and almost all other such experiments, to be carried out, and the results to be obtained, in Germany. We shall get them after they have passed through the patent office and shall, very likely, soon be making large quantities of ethyl alcohol from wood, paying royalties to Germans for the privilege.
The suggestion has been made that a process for the manufacture of alcohol might be run profitably in conjunction with wood-pulp paper mills. There does not appear to be the least chance of utilizing the waste from the end of the sulphite process because it contains little or nothing fermentable. It has already been subjected for a long while to the action of sulphurous acid and the fermentable sugars, pro-
