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T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y .
although there is an indication that the strength of the acid is riot sufficiently great for highly ferruginous soils. It is generally considered that apatite (soluble in N/5 HCl), and wavellite and dufrenite (soluble in I per cent. NaOH solution), constitute the principal mineral phosphates of the soil (soil No. IO may contain some triplite), and yet the combined P,O, dissolved by the two solvents, constitutes but a small percentage of the total phosphate in the soil. It is true that the dissolving power of a given solvent toward a pure chemical may be greatly modified when the same body is associated with numerous other substances, such as occur in soils. Furthermore, these soils contain a large percentage of finely divided ferric hydrate which so permeates and surrounds the soil particles that a complete dissolution can be brought about only by use of agents that are capable of dissolving the iron also. It’ has been suggested that the amount of P,O, recovered from a soil by the use of a given solvent is not a true measure of the dissolving power of this solvent towards the phosphates in the soil, since some of the P,O,, after being dissolved, is refixed by the soil. In this connection it has been shown that these soils possess a high fixing power for soluble phosphates. It seems more likely, however, that only a small percentage of the phosphates present was dissolved by the solvents employed. We should expect soils which contain from ten to twenty times as much iron and alumina as calcium to hold the phosphoric acid, combined largely with iron and alumina, rather than calcium; and the behavior of crops on these soils, together with their solubility, indicates the correctness of this view.
June, 1910
ters may be connected in series by rubber tubes 25 to 30 cm. long, and the water run through the series from first flask to last. There is no loss of digesting liquid by evaporation; and if the boiling is started and conducted slowly, no great trouble from’foaming, since each digester may, without distprbing its neighbor, be lifted and swirled. Figures 3, 6, 7, 9 show suitable forms of filtersbroad mouth tube, funnel, thistle tube-each provided with a rim or flange over which the linen disc is drawn taut. Convenient dimensions of these tubes (Figs. 3, 7 ) are, large end, diameter 5 to 6 cm., length 6Lto 9 cm.; total length, including stem, 18 to
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I
20 cm; diameter of stem, inside, about 0 . 5 cm. The rim or flange should be about 0 . 5 cm. wide, turned a t nearly right angle to the axis of the tube or funnel and uniform in diameter. Note the rims (Figs. 3 and 6). The linen disc (Fig. 4) is attached to the tube by means of a strong, but not too coarse, flax thread. This thread is passed in short running stitches through the linen in a circle (Fig. 4) whose [CHEMICAL LABORATORY, KORTHCAROLIHADEPARTMENT OF diameter is greater than that of the rim of the tube AGRICULTURE.] (or funnel), but not so much greater that, when the A RAPID METHOD OF DETERMINING CRUDE linen is drawn over the rim and the thread tied, it FIBER. (the thread) will press against the side of the tubeBy J. M. PICKEL. the entire “pull” of the thread should be exerted Received January 1 7 , 1910. This is, in the main, a method of filtering and on the linen. This adjustment is easily made once washing the fiber. The filtration is effected by for all, and permanently fixed in the shape of a pasteupward suction of the fiber against linen. The method board (or metal) disc (Fig. 5) which shall serve as a was first used by the writer in the summer of 1902, pattern; any needlewoman can then make the linen since when it has been in constant use in this labora- discs by the score or hundred, according to need. tory. A bare outline of the method was published As each linen will serve for a half dozen or more fiber determinations, these filters are inexpensive. In in Science (Jan. 8, 1904). Figure I (accompanying illustration) shows the addition to the larger filter, 5 to 6 cm. diameter, a manner of digesting the fiber: a beaker 7 to 8 cm. in smaller one, diameter about 2 . 5 cm., is needed. A diameter, about 15 cm. deep, capacity 600 to 800 cc., perfdrated disc (copper) over the mouth of the covered by a round-bottom flask through which flows tube, under the linen, is useful but not indispensicold water. Any convenient number of such diges- ble. Ofieration.-The filter having been connected by * Fraps, LOC.cit.
MACNIDER O N THE DETERLWINATIOLVO F CRUDE FIBER.
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heavy rubber tube to a Bunsen suction pump and per cent., 0.26 per cent., 0 . 2 7 per cent., 0 . 3 5 per cent., suction turned on, the surface of the filter is put in 0 . 4 6 per cent., respectively, of solids which had passed contact and kept in contact with the surface of the through the linen. liquid in the beaker (Fig. 2) until all the liquid is The filtering (from the second or alkaline digestion), drawn into the filter-tube, when the latter is with- washing and transferring of the fiber to the evaporadrawn and reversed (Fig. 3) to permit the liquid to ting dishes in the case of six cocoas consumed sixtybe sucked out. The suction is then discontinued, six minutes, an average of eleven minutes to the dethe fiber washed with 50 to 75 cc. of boiling water termination ; the filtrates from these determinations back into the beaker, stirred thoroughly, allowed, if were then put through hardened filter paper under need be, to subside a few moments, and the liquid suction, the shortest time of filtering in any of the sucked out through the filter, as above described. six cases was one hour, the longest seven hours. Three or four such w.d,ings will free the fiber of acid The above tests of the method were made several or alkali. When freed of acid, the fiber is washed years ago. The author has hoped from year to year back into the beaker with the requisite quantity of to make more extended and searching experiments, 1.25 per cent. alkali and digested. Finally, when but has not been able to do so. filtered and washed (as above described) free of alkali, The official method of the U. S. Dept. of Agr. (Bur. the fiber is washed with distilled water into a 50 cc. of Chem., Bull. 107, p. 56, revised) for crude fiber tared evaporation dish (royal Berlin porcelain in says : " Filter through linen, asbestos or glasswool "absence of platinum) , the water evaporated on steam nothing as to particular grade of linen. One naturally bath, the fiber dried, weighed, incinerated, the ash selects, if linen, that of finest, closest mesh obtainaweighed, the fiber obtained by difference in the usual ble. Old filters of the author, still on hand, are 32 x way. A small flexible steel spatula is often useful in 32 per square cm., that is, contain about thirty-two removing the fiber from the linen and in bringing it threads each way to the cm.; the threads are apparinto the dish. It will not infrequently happen that ently about 0 . 2 to 0 . 3 mm. in diameter. Undoubtthe dish will get full of water before all the fiber is edly standard, or better standwdized linen-if that washed into i t ; in such case, the excess of water is material be finally found to be best-should be removed by suction through the small filter above adopted. referred to. There is a kind of felt, composed mainly of cotExperiments with filtering materials other than ton, comparatively thin, uniform in texture; it would linen-hardened filter paper, flannel, chamois skin, probably make an excellent filter. It is to be had unglazed porcelain discs (Fig. 8) were made--but the a t tailoring establishments. first and last are out of the question because of slowRALEIGII,N. C . . Jan. 10, 1910. ness, the two others are not suitable with hot alkali. d 3 \ I I Results Obtained by the Method.-Duplicates on \'THE DETERMINATION OF CRUDE FIBER. peanut hulls, corn bran, rice chaff, corn cobs, and peaBy G. M . MACNIDER. nut middling's gave results differing by 0 . 0 1 per cent., ? { Received February 1 7 , 1910. 0 . 1 4 per cent., 0 . 3 2 per cent., 0 . 2 0 per cent., 0 . 1 2 In carrying out the method of the A. 0. A. C. for per cent., respectively. I n the case of six samples of cocoas, duplicates were obtained differing by the determination of crude fiber in cattle feeds' we have tried a good many modifications of the appa0 . 0 2 per cent., 0.33 .per cent., 0 . 0 3 per cent., 0 . 0 2 per cent., 0 . 0 6 per cent., 0 . 1 3 per cent. in each case. ratus to shorten the time required and to make the The fiber of cocoa, a fine powder, is one of the most determination less laborious. As the apparatus in difficult to filter and wash-next to impossible with a use in this laboratory a t present has proved satisGooch filter, but comparatively easy and quick by factory, some of the modifications in use may be of interest to chemists engaged in agricultural work. this method. The digestions with I .25 per cent. sulphuric acid The filtrates and wash-water from the second or alkaline digestion were, after having passed through and 1 . 2 5 per cent. sodium hydroxide are done in the linen filter, put through gooches (asbestos). It 600 cc. Jena glass beakers, 16.5 cm. in height and with was found in six fiber determinations (wheat bran, a uniform diameter of 8 cm. During the digestion shorts, cornmeal, " ship stuff ") that the gooches a clock glass is placed over the beaker to condense retained 0 . 2 1 per cent. to 0 . 3 7 per cent. of solids, the steam. This is fairly satisfactory, but considerareckoned as fiber, that had passed through the linen; ble trouble is frequently caused by the frothing of in the case of seven cocoas, filter paper (the hard-ned the liquid, thereby necessitating the washing of the Bureau of Chemistry. Bull. No. 107 (revised). variety) retained o 0 2 per cent., 0 . 0 2 per cent. 0 . 0 2 1
