the freight costs for wet pulp would be prohibitive, and the pulp besides would run the risk of turning mouldy in transit.

The number of mechanical pulp mills in Sweden are now 88, but of these, 18 are operated in connection with board mills and 33 with paper mills. Of the 37 mills producing pulp for sale the largest are situated in Norrland, and represent 65 per cent of the total production. Many of the mills in Central and West Sweden have a comparatively small output of which a large proportion is dry pulp. The latter category of mills are almost without exception built immediately at the waterfalls, where cheap power is obtainable, because electric transmission would come more expensive. Some of the lately built mechanical pulp mills in Norrland, however, buy their power from electric power works at some distance, but this is compensated to some extent by their situation on the coast which relieves them of paying railway freight to the port of shipment.

Chemical Woodpulp (Cellulose)

The two principal varieties of chemical pulp are sulphate and sulphite cellulose, the former being produced by using an alkali solution, and the latter a sulphur solution for releasing the fibres of the wood from the substances in which they are imbedded.

Sulphate cellulose. This pulp is manufactured and sold either as bleached or unbleached sulphate. Of the unbleached sulphate there are two qualities, easy-bleaching and strong; the latter also called Kraft pulp. The easy-bleaching sulphate is boiled in a stronger lye and under higher pressure, a process that produces purer fibres and makes it possible to bleach the pulp by means of chloride of lime. The Kraft pulp, on the other hand, is boiled in a weaker solution and with a lower pressure which is less hard on the fibres and makes them stronger. This process was invented by a Swedish engineer, Alvar Müntzing. The pulp in question is used for making the famous Kraft papers. Of recent years the demand for Kraft pulp has increased enormously, especially from the United States, so that fully 80% of the Swedish production of sulphate is composed of Kraft pulp.

Only an insignificant portion of the sulphate is bleached at the mills, the demand for such a grade being both small and fluctuating.

A defect inherent in sulphate cellulose, which strongly restricts its utility, is that the fibre undergoes a sort of oxidation during the cooking which gives the pulp a brownish tint. In the unbleached state it can therefore only be used for brown paper. The bleached sulphate is used for making certain fine grades of paper having a soft and full texture.

In Sweden sulphate cellulose is only produced nowadays from coniferous wood, both spruce and pine, and the great advantage of this method is that the waste from the sawmills can be utilized as well as damaged wood from the forests. As a method for effecting economies in the entire wood products industry the process is therefore of the utmost importance.

The soda pulp production was introduced in Sweden already in 1871, when first the Delary and later some other mills were built. The sulphite process following close upon it, however, a stagnation set in after the first period of activity, but by means

of improved methods in the production and, above all, by the invention of the Kraftpulp process, a renaissance has set in in this branch of the industry.

The production of sulphate cellulose in 1920 amounted to 204,629 tons, valued at 96.6 million kronor, and the export reached a quantity of 140,570 tons valued at 77-1 mill. kr. During 1922 the export amounted to 207,462 tons.

The Swedish paper mills consume about 30 per cent of the total production, and this goes almost entirely to the manufacture of Kraft paper.

The countries beside Sweden who export sulphate cellulose are Finland, Norway, and Canada. The respective export figures for the year 1920 are given below.

Great Britain, the United States, Germany, and France have in the past been the principal consumers of Swedish sulphate cellulose. Owing to the depression in the European trade in the years 1921 and 1922 a certain change has taken place in this situation, inasmuch as the export to the United States has increased quite considerably. There are in Sweden at present 26 sulphate mills with a normal output of about 250,000 tons of dry pulp. Of these 9 mills are operated in connection with paper mills. The greater number, and the largest of the mills manufacturing sulphate celloluse for the open market, are situated in Norrland.

The cellulose fibres represent only about 50 per cent of the substance of the dry wood, while the remaining 50 per cent are composed of other carbo-hydrates, lignines, fat, rosin, and proteins, which remain in the lye after the cooking. The sulphate mills concentrate and burn the lye in order to recover the soda, and the heat generated by this process is utilized, and is sufficient not only for carrying out the process itself, but in modern plants there is a surplus of heat for other purposes in the works. Of by-products recovered during the cooking, and before the concentration takes place, may be mentioned methyl alcohol, turpentine, liquid resin, and certain oils. The value of such by-products in 1920 amounted to 1,879,830 kronor.

Sulphite cellulose. This product is like sulphate cellulose supplied as unbleached and bleached, and of the former there are two distinct grades: easy-bleaching and strong sulphite.

Of the total sulphite production of Sweden about two-thirds are composed of strong sulphite, and about one-third of easy-bleaching, of which about 35 per cent is bleached at the mills. Many paper mills, especially in England, buy easy-bleaching sulphite and bleach it themselves.

Only spruce can be used for the manufacture of sulphite. Pine contains great a deal of rosin, and the sulphuric acid used in this process does not liberate the fibres properly on this account. Deciduous wood is also unsuitable on account of its short fibres. As mentioned above, sulphite pulp was first produced on a commercial scale in a NorthSwedish mill, and the sulphite industry has ever since proved very attractive and has expanded enormously in Sweden. Sweden now occupies the first place among the

sulphite producing countries in Europe, and is only surpassed by the United States in the matter of quantity produced. The quality of the Swedish sulphite has the very highest reputation. Sulphite mills are scattered practically all over the country. The largest and most important ones, as might be expected, are situated in Norrland, and usually at the river mouths in connection with the sawmills. This naturally is of advantage for the floating of the timber, direct unloading of the pyrites, lime, coal, etc. at the mills, and the shipment of the ready product without intermediate railway or water transport. The production of sulphite cellulose in 1920 amounted to 769,004 tons valued at 419-7 mill. kronor, and the export to 577,280 tons valued at 337.5 mill. kronor. In 1922 the export had risen to 687,403 tons.

The Swedish paper mills are estimated to consume in normal times about 180,000 tons of sulphite.

The following countries besides Sweden are exporters of sulphite, and accounted for the following quantities in 1920:

The Swedish export of sulphite is therefore close upon half of the total, and, when it is considered that practically the whole of the Canadian export is absorbed by the United States, the fact becomes still more significant.

Great Britain, France, and the United States are the principal buyers of the Swedish sulphite, the three countries taking about 70 per cent of the total export from Sweden. The number of sulphite mills in Sweden is at present 66 with an annual output of about 875,000 tons. 27 of these mills are operated in conjunction with papermills. As in the case of sulphate, the sulphite lye contains 50 per cent of the dry substance of the wood after the pulp has been removed. This liquid was earlier allowed to escape into the rivers with many deleterious results besides the waste occasioned thereby. The fish in the rivers and waters outside was threatened with extinction for one thing, and the water fouled. From the first many attempts have in consequence been made towards utilizing the useful substances contained in the liquid, and in 1909 the Swedish engineers G. Ekström and H. Wallin discovered a practical method for extracting spirits from the fermentable carbo-hydrates contained in same. A great number of installations were built at the mills, especially during the years 1918-1920, for utilizing this invention, and at present 22 sulphite-mill spirit factories with a total annual capacity of 20,000,000 litres of 95 per cent spirit are in operation. The difficulty of disposing of such a large quantity, however, has restricted the output of late years to something like 6,000,000 litres per annum.

The enormous expansion of the woodpulp industry is one of the most characteristic features of the general economic development of Sweden during the last few decades. The total value of the Swedish industrial production in 1920 was estimated at about 6,730 mill. kronor, and, of this total, wood pulp accounted for 616 mill. kr. or 9-15 %. As regards exports woodpulp occupies a more dominating position, being in 1920 first among Swedish export commodities and surpassing woodgoods, the figures being 475,144,000 kr. for woodpulp and 469,865,000 kr. for woodgoods, or respectively 20-86 % and 20.62 % of the total exports from Sweden.

The table below gives the figures for both the total exports, and the wood pulp export in value and per cent showing the strong advance of this commodity both absolutely and in proportion to the rest.

The number of workers in the woodpulp industry was in 1920 19,614 with a staff of 595 persons. The power supplied in the same year for operating the mills amounted to 170,795 horsepower of which 41,056 hp. were obtained from steam plants. The fuel consumption during the same year amounted to 113,712 tons of coal, 5,511,985 cub. metres of wood or chips, and 683 tons of liquid fuel which, reduced to the fuel value of coal, represent 743,996 tons of coal. This consumption falls almost entirely on the chemical pulp industry which is a particularly large consumer of fuel. The total annual fuel consumption in Sweden for industrial purposes, computed in coal, amounts to 3,305,041 tons, which makes the quantity required for the cellulose industry not less than 22 1⁄2 per cent. It is to be noted, moreover, that the above figures do not include the consumption of the woodpulp and cellulose mills owned by and operated for papermills.

The importance of the wood pulp industry for a rational method of forestry cannot be overestimated. Originally the lumbering was restricted to large trees suitable for being sawn into commercial woodgoods. This gradually reduced the value of the woods at a quicker rate than necessary nowadays, as many stunted and damaged tree were left standing which could only partially make use of the increased supply of nourishment. Plants and mosses also germinated which prevented fresh trees from taking root. Neither was it a good policy to let the growing wood take care of itself because, as soon as the trees reach a height were they take away the light from one another, a fierce struggle sets in, and the weaker trees gradually have to give way. A great deal of timber is lost in this way, and even the growth of the surviving trees is retarded from the long and hard battle for supremacy.

In order to remedy these matters the forests must be thinned at regular intervals. The gain is also that the mixture of the wood can be planned from the start, so that the growth is always maintained at the highest level, and the full productive capacity of the land utilized. A condition for such forestry on rational lines, however, is that small and stunted trees can be disposed of at fair prices. Here is where the woodpulp industry is of the greatest value by consuming all timber not usable by the sawmills; the tops of the large trunks as well as all kinds of smallwood obtained from the forests.

Concerning the further development of the woodpulp industry in Sweden it has often been said that it would soon reach its high-water mark as the capacity of the forests to supply more pulpwood could hardly be counted on. Rather large dimensions of spruce are now used for making woodpulp, and then it becomes a question of competition between the sawmills and the pulp mills for the timber. In the other Scandinavian country, Norway, the latter industry has already been victorious in the competition. In Sweden there is every reason to expect that the woodpulp industry will continue to expand for a good while as the principal object is to obtain the greatest yield from a certain plot of forestland and not the greatest number of logs fit for being sawn into deals and boards.

Karl Nyström