be treated is the first consideration, since this grass differs materially in character in the different countries from which it is imported. Spanish esparto is considered the best for paper-making, as it is stronger in fibre and yields a whiter pulp than other varieties. Of the African espartos there are several varieties, which are known respectively as Oran, Tripoli, Sfax, Gabes, and Susa. Of these, the first-named (Algerian esparto) is held in highest estimation amongst paper-makers, since it more closely resembles Spanish esparto than the other varieties, though not so hard and stiff as the latter. These grasses usually have a length of about 10 to 12 inches. Tripoli esparto has an entirely different growth, being sometimes as long as 2½ or 3 feet, and proportionately stouter, and is also softer than Oran esparto, which is not so hard as the Spanish variety. Tripoli esparto does not yield a strong paper by itself, but in conjunction with Oran esparto gives more favourable results. Sfax and Gabes espartos have a closer resemblance to Oran than Tripoli, but are not so strong as Oran, being green and spongy, and not so dry as the latter variety. Susa esparto of good quality is said to equal Oran, but not to yield so high a percentage of fibre.
The next important consideration is to determine the percentage of caustic alkali which should be used per hundredweight of the particular variety of esparto to be treated, and we cannot do better than give the following proportions recommended by Mr. Dunbar.
| Fine Spanish | 18 to 20 | lbs. of | 70 per cent. | caustic soda | per cwt. |
| Medium Spanish | 16 to 18 | " | " | " | " |
| Fine Oran | 18 | " | " | " | " |
| Medium Oran | 16 to 17 | " | " | " | " |
| Susa | 18 | " | " | " | " |
| Tripoli | 19 to 20 | " | " | " | " |
| Sfax | 20 to 21 | " | " | " | " |
Mr. Dunbar says that the above figures "insure a first-class boil, with the steam pressure of 25 lbs. and not exceeding 30 lbs., but are liable to alteration according to circumstances—such as the form of boilers, quality of the water for boiling purposes, and steam facilities, which ought at all times to be steady and uniform to get the absolute regularity required."
Respecting the strength of caustic ley used for boiling esparto, as indicated by Twaddell's hydrometer, this appears to range from 7° to 15°, some preferring to boil with stronger liquors than others. The time occupied in boiling also varies at different mills, and depends greatly upon the character of the boiler used. We are informed that a Sinclair boiler will turn out, on an average, three boils in twenty-four hours, including filling, boiling, discharging, &c., the boiling occupying about four hours for each batch of grass.
The boiling being completed, the liquor is run off into tanks, to be afterwards treated for the recovery of the soda, and the esparto is then subjected to a second boiling with water only for about 20 minutes. The liquor from the second boiling is sometimes thrown away, even when the soda from the first liquor is recovered; but a more economical method is to use this liquor, in lieu of water, strengthened with soda for a first boiling; or to mix it with the first liquors and evaporate the whole together. The second boiling being finished, the steam is turned off, and water then run in and steam again turned on for a short time, and the water then run off and the esparto allowed to drain thoroughly. The boiled grass is then discharged into trucks which convey it to the washing engines.
The liquor resulting from the boiling of esparto, which is of a dark brown colour, contains nearly all the soda originally used, but it also contains silicious, resinous, and other vegetable matters which it has dissolved out of the grass, the silica taking the form of silicate of soda. The esparto liquor, which was formerly allowed to run to waste, polluting our rivers to a serious extent, is now treated by several ingenious methods for the recovery of the soda with considerable advantage alike to the manufacturer and the public. The process consists essentially in boiling down the liquor to dryness, and incinerating the residue. During the process of incineration the carbonaceous matter extracted from the grass is converted into carbonic acid, which, combining with the soda, reconverts it into carbonate of soda, which is afterwards causticised with lime in the usual way, and the caustic soda thus obtained is again used in the boiling of esparto. Although one or other of the "recovery" processes is adopted at a good many of our paper-mills, the recovery of the soda is by no means universal as yet, but the time will doubtless soon arrive when the economical advantages of the process will be fully recognised. Indeed, we know it to be the fact that some manufacturers are watching, with keen interest, the progress of some of the newer systems of soda recovery, with the full intention eventually of adopting one or other of them.
Washing Boiled Esparto.—This operation is usually performed in engines similar to those used in washing rags, but in some mills the boiled grass is washed in a series of tanks, so arranged that water flows in at one end of the series, thence passing in succession through each batch of grass in the other tanks, and finally issues at the farthest end of the series as a very concentrated liquor. By this arrangement there is great economy of water, while at the same time no loss of fibre occurs. The concentrated washing liquors thus obtained may be evaporated, and the alkali recovered, which would be an undoubted saving, since these liquors obtained in the ordinary way by washing in the boilers are generally run off as waste. The engines used for washing esparto and converting it into half-stuff are generally of large size, and capable of treating a ton of boiled esparto. In this engine, however, there is no bed-plate, as the action of the roll alone is sufficient to reduce the boiled and softened esparto to half-stuff. A drum-washer is also furnished to the engine, which carries off the dirty washing water, while an equivalent proportion of clean water is kept constantly running into the engine from an elbowed pipe at its end. In charging the washing-engine, it is first about three parts filled with water, when the washing cylinder is lowered, and the esparto is then put in, care being taken not to introduce more of the material than will work freely under the action of the roll; if the mass be too stiff, portions of the material may be imperfectly washed. While the washing is in progress, the workman, armed with a wooden paddle, constantly stirs the esparto, clearing it away from the sides of the engine, so that none of the material may escape a perfect washing. At the bottom of the engine is a "sand-trap," covered with perforated zinc, through which any sand or other solid particles which may be present escape. When the washing is complete, the fresh water supply is shut off, and the drum-washer allowed to run until enough water has been removed to make room for the bleaching liquor.
Young's Process.—By this process the boiled and strained esparto is passed through elastic covered rollers, so adjusted as to split up and squeeze out the dissolved matters or liquid from the fibres, thus leaving them clean and open for the access of the bleaching liquor.
Bleaching the Esparto.—It is usual to bleach esparto in the washing engine, for which purpose a tank of bleaching liquor of the required strength (about 6° T. for Spanish) is placed close to the engine, which is provided with a pipe leading to the
