I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
168
Table I-Commercial COAL
No.
East Kentucky, Harlan Co.
691
Pennsylvania, Pittsburgh Seam
750
Alabama, Mary Lee Seam
975
Southern Illinois, Franklin Co.
1122
Central Illinois, Vermilion Co.
883
Indiana Fourth Vein, Vermilion Co.
634
Per ton of coal of 2000 Ibs.
Vol. 21, No. 2
Yields, Midtemperature Coking Processo
FIXED
ASH MOISTUREVOLATILE CARBON Per cent Per cent Per cent Per cent 55.95 4.84 2.30 36.90 57.27 4.95 Dry 37.77 55.37 8.99 1.40 34.23 56.16 9.12 Dry 34.72 56.40 12.99 2.70 27.91 57.97 13.35 Dry 28.68 50.00 8.40 7.50 34.10 54.05 9.10 Dry 36.85 40.80 12.00 10.20 37.00 45.44 13.36 Dry 41.20 44.77 6.81 13.42 35.00 51.71 7.86 Dry 40.42
(3). The gas yield at this temperature is substantially all that IS available a t any temperature, measured in terms of heat units-that is, for coals of the Illinois type, 5 '/z t o 6 million B. t. u. per ton. At higher temperatures the volume of gas may be greater, but the heat value per cubic foot will be less. (4) The tars, not having been subjected t o such violent secondary decomposition, are larger in amount, more uniform in composition, and of greater value, owing to the higher percentages of the active principles, the creosote oils, required in wood preservation. Their specific gravity is greater than 1.1; hence they readily separate by gravity and are drawn off as dry tar-that is, with less than 3 per cent of water present. ( 5 ) By strict observance of the fundamental principles already demonstrated by the temperature logs of carbonization at different rates as t o time and reproducing the zonal reactions separately, the theoretical time for the actual carbonization process should be within 3l/2 t o 5 l / 2 hours. This can best be illustrated by referring again t o the timetemperature charts already shown. I n Figure 1 the active process of decomposition in test 11 obviously begins a t about 350' C. Assuming, now, t h a t the most desirable results are secured when a temperature of 750' or possibly 800' C. has been attained, we have 4 t o 41/2 hours for the actual time of carbonization.
Midtemperature Coking Experimental Plant These conditions have been strictly observed in the experimental plant operating as shown by the accompanying photographs and figures. This plant has been operating con-
COKE
Lbs. 1319 1350 1350 1371 1459 1500 1249 1350 1153 1284 1125 1300
TAR Gallons 17.0 17.4 16.0 16.2 9.73 10.00 13.0 14.0 14.2 15.8 10.4 12.0
GAS Feet 8050 8242 8700 8840 8136 8360 8215 8881 7833 8723 7305 8438
GAS PRODUCTION Av. per Total cu. f t . perton
B. 1.
u.
700 700 700 700 650 650 650 650 650 650 650 650
B. t .
Y.
5,636,000 5,769,000 6,095,000 6,180,000 5,288,250 5,435,000 5,340,000 5,773,000 5,091,660 5,670,000 4,748,910 5,486,000
tinuously 24 hours a day for 365 days. A preliminary or conditioning temperature below the softening point of the coal was regularly employed. The carbonization reactions were complete a t from 750" to 800" C. and within a time limit of from 4 to 5 hours. Secondary ,decomposition effects on the hydrocarbon vapors were definite, resulting in a gas'of slightly lower volume but of thermal value substantially equivalent to that produced by the standard high-temperature process. There was a corresponding increase in the condensable products, the tars proving to be remarkably uniform and of exceptionally high grade for creosoting purposes. Naphthalene formation was very slight. The coke was dense, firm, and of exceptionally high quality, especially conforming in combustion properties to the ignition temperatures shown in Figure 9. The oven employed was of standard type as manufactured by the Russell Engineering Company, of St. Louis, now the Improved Equipment-Russell Engineering Corporation, New York City. Experiments were conducted on carlots of coal from as far west as Iowa, as far south as Birmingham, Ala., and from the Pittsburgh and Cambria County seams in the East, with substantially all types from eastern and western Kentucky, Indiana, and Illinois. Without exception a highgrade coke was produced. Typical examples showing the amount and character of the yields are given in Table I.
Identification of Rayon' Wm. D. Grier* 150 WILLIAMST., NEW YO=, N. Y.
H E phenomenal growth of the so-called artificial silk, or rayon, industry in the last few years has developed a need for simple and accurate methods for the identification of the various types now on the market. Methods detailed in much of the recent literature seem to have been developed from work upon paper-making materials and, while of undoubted value in the identification of the various fibers used for that purpose, especially in the differentiation of chemical and ground wood, rag stock, lignified or unlignified fibers, and the like, give uncertain results in the study of rayon. A careful trial of many of the methods suggested indicates that tests of a purely chemical nature, dependent on color reactions with such reagents as Heraberg's reagent, solutions of iodine in potassium iodide, either with or followed by sulfuric acid, together with those depending on afinity for certain types of dyes, are, with one or two exceptions, inconclusive.
T
1 2
Received September 7, 1928. President, The New York Microscopical Society.
Comparatively few of the writers on the subject have laid much stress upon the use of the microscope, although Chamot, Behrens, and others have demonstrated that methods of combined microscopical and chemical analysis are of the highest value in the examination of technical materials. With this thought in mind the writer, after examination of authentic samples of practically all the leading types of rayon now on the market has arrived a t the conclusion that their characteristics, as exhibited under the microscope (subject in one or two cases to a simple chemical test of a confirmatory nature) are sufficiently constant to afford a reasonably certain means of identification. For. the sake of brevity it will be understood that whenever the appearance or structure of a rayon fiber is mentioned in this article, it means its appearance as exhibited under a moderate magnification of 200 diameters more or less, by transmitted light, mounted in a drop of distilled water, under a cover glass of medium thickness, and in either side view or transverse section.
INDUSTRIAL AND ENGINEERING CHEMISTRY
February, 1929
169
a preliminary examination will indicate the presence of cotton, linen, wool, or silk by their characteristic appearance, which is quite different from that of any variety of rayon. (Figure 1) Cotton is shown as a rather flat filament, more or less twisted on its own axis; linen as a fine straight filament with numerous irregular cross marks or nodes; wool is more or less curly, cylindrical in cram section, and covered with very fine scales or imbrications, sometimes rather difficult to see without careful illumination; natural silk is B fine, straight, glassy filament with no marks or visible structure. In doubtful cases the presence of wool or natural silk may be immediately demonsm.ted by Millon's reagent (dissolve mercury in its own weight of strong nitric acid and dilute with an equal volume of water). Xaving identified any natural fiber that may be present, we have next to identify the particular types of rayon. Identiflcation of Type of Rayon Figure I-TezriIe
Fibers. Approxfmateb 125 X
There are a t present four general types of rayon on the market, manufactured either from a cutton linter or woodpulp base by radically different processes-namely, viscose, Chardonnet or nitro silk, cuprammonium, and the acetate silks. The first three are generally classed as reverted celhiloses, while the fourth or acetate silks are acetic acid esters of cellulose. It is reported that investigations are in progress with a view to development of a formyl cellulose, although no such material bas appeared in this market as far as the writer is aware. In many cases rayon receives a finishing treatment with textile oils, or emulsions, and processes involving furt.her chemical treatment for delustering and crinkling are in use. I t would seem quite possible that fibers so treated might react differently from untreated material when subjected to chemical tests, although their appearance under the microscope might he unaltered. Microscopical methods are peculiarly serviceable in cases where only a small amount of material is available. Before proceeding to the examination of material of an unknowii nature, the investigator should familiarize himself with the appearance of the various types of rayon by examining samples of known origin; and it will he found that there will be little dficulty in identifying the differentGwes by a visual examination under the microscope, using the few and simple chemical tests mentioned below for confirmatory purposes, if needed, although in many cases they will not be required. Identification of Rayon from Other Fibers
For the qualitative microscopical analysis of a textile fabric a few square centimeters should be unraveled, keeping the warp and tilling, or the different kinds of fiber if more than one, separate. In thecnse of dyed material the coloring can be stripped, ifnecessary, by the use of sodium hydrosulfite, followed by thorough washing. In the cnse of mixed fabrics
Figure 2-Type
Figure 5-Type
A
A
Acetate types, such as Celanese or Lustron (the latter is no longer manufactured), are glassy translucent filaments somewhat flattened, and with few or no surface grooves or corrugations. The filaments are of irre&%lar cross section with comparatively few indentations (Figures 8 and 9). When examined between crossed Kicol prisms the fibers polarize very feebly, showing little if any color, being markedly different from other rayon fibers in this respect. The material is immediately soluble in acetone. Chardonnet or nitro silks somewhat resemble the acetate types, but have practically no surface marks and fewer indentations in cross section being, roughly speaking, kidney shape (Figures 10,11, 13, and 20). Nitro silks give a bright sapphire-blue color, afterward dissolving, io a solution of diphenylaminein sulfuric acid (1.57 grams diphenylamine in 25 ml. sulfuric acid). This is a very certain and sensitive test, as other rayons dissolve without changing color. The fibers polarize brilliantly with a varied play of colors between crossed Kicol prisms, especially when a selenite plate is used. Viscose rayons have an entirely different appearance from any other type and should he immediately recognizable. They occur in two rather marked modifications-a flattish or ribbon-like filament (Figure 31, and a more rounded type
B
~i~~~~3-rype
Figure +--Type
A
Vischse of Sir Different Makes cross sections, x 250
Figure +-Type
Figure ?-Type
A
A
170
INDUSTRIAL AND ENGIAr8ERING CHEMISTRY
(Figures 2, 4, 5, and 6 ) . I n both cases they are deeply grooved and scored longitudinally, with numerous air bubbles or incjusions @igures 15, 16, and 17), and of a very and irregular cross section, deeply indented (Figures 2 to j and 18). The so-called "macaroni" or tubular type of viscose, known as "celta,,, is easily distinguislied by the large and ll~meronsair bubbles contained when examilled in drop of water, and tlie cross sections which resemble a more or less collapsed tube with numerous sudace grooves and corruga. tions (Figure 14). All types of viscose polarize brilliantly.
Vol. 21,
KO.
2
Study of Cross Sections of Rayon Fibers
The study of cross sections of the synthetic t.extile fibers is of considerable importance, not only as a means of identification, but also in the study of the effect of various dyestliffs,methods of spinning, and coagulating or setting baths. T h e cross sections arc readily made with the aid of one of tile CllfRPCI' types Of so-called "students microtomes." The iihers to be examined should be tied at each end in a Sinall buiidle about the thickness of a lead pencil and about 2 em. long. They may then be stained or dyed in an aqueous solutioir, about 0.5 per cent streiigth of some suitable dye such as Congo rcd, safranine, or cryst,al violet, washed, airdried, and immersed for 20 minutes or so in paraffin, kept a t a little above the melting point (about 48" C.) on the water bath, care being taken not to omrheat. Tlic sample may then be imbedded in the usual way in it paraffin block. As soon as the paraffin has set, the block should be dropped into cold water, where it should reqiain for at least 2 hours, or uiitil ready t o cut. This is very important, as the paraffin will crystallize if a,llowed to cool slowly, and the block will be liable to crumble when cut. The block may then be trimmed with a sharp knife, so as to. enclose tho sample in a block about 1.5 or 2 em. cube, which Figure 8-Acetate Silk. Type 1 Fipure 9 - ~ c e i r l e Silk, Type 2 may then be attached t o one of the small fiber blocks supplied for the purpose, by means of a drop of meltcd paraffin. The block is then ready to be placed in the object holder or clamp of the microtome, orientated so that the sections taken will be at right angles t o the length of the fiber. The microtome knife must he kept very sharp by. frevuent stroo. ping, as cutting these fibers seems io d u l l ~ h eedge much m o k rapidly than in the case of animal tissues. Proper and careful trimming of the block beforo mounting will materially assist in tho proper cutting of the sections. IS the sectious curl up, tire room temperature is too low; if t h y crumble OT become sticky, t.lie room temperature is, too high. The temperature in the viciniby of t.lie kniSe should he about io" F. (21" e.),and if the sections tcnd to curl up, air ordinary 40-watt Mazda lamp placed near the block for. Figure 10-Chardonnet Silk Figure ll-Cupmmmoiiiurn Silk a few moments will generally remedy the trouble. Various Tynes of Rayon Cross Sections. x 250 The edge of the knife s2rould be at right angles to the direction of motion, although sometimes better re~iiltscan beCuprammonium silks resemble natural silk more than the secured at an angle of about 60 degrees. This is best deterothers, being very smooth and glassy in appearance, widhout mined by a few trials. Generally speaking, in cutting paraffin any surface grooves or corrugations (Figure 12) and a fairly sections the action slrould be more like that of a plane than regular cross section without any indentations (Figures 11 a drawing cut. The paraffin sections should be affixed to. and 19). Cuprammonium fibers polarize with extreme slides with Mayer's fixative (fresh egg albumin 50 cc., glycbrilliancy, the play of colors being very marked. Great erol 50 cc., sodium salicylate 1 gram), dried, the paraffin difficuky has been experienced in devising any strictly cliemiwashed out with xylene, tlie xylene washed out wit,ti nlcohol, cal tests for differentiating between viscose and cuprammoniid mouiited in Canada balsam. nium. The most simple and reliable seems to be that snggcsted by Schreiber and Hamm,3 which depends upon the Apparatus Required for Microscopic Work detection of minute residual amounts of sulfur compounds in viscose, when heated over the steam bath in very dilute I n the microscopic examination of rayon, care should besulfuric acid. taken to see that the illuminating apparatus is correctly As far as the writer bas been able to determine, the charac- eenkred, the condenser focused, and that the source of illu-. terist.ic appearance of the various rayon fibers, particularly minationisnot too strong. Anordinary40-watt FrostedMazdR in cross section, seems to be peculiar to the process of manu- bulb about a foot from the mirror is ample illumination for^ facture in each case and constant in the various types of all ordinary purposes. Too much light or poorly centered which authentic samples were available, comprising Twcose ' apparatus is liable to give false images and erroneous imfrom nine different manufacturers, two makes of acetate pressions, showing lines or markings that do not exist. silks, two makes of nitro silk, three samples of cuprammoNo great financial outlay is required. All that is needed is. nium, as well as numerous samples of fabrics and yarn of an a good solid microscope stand of one of the moderate-priced unknown origin purchased or obtained in open market. I n types which are built by all the leading makers. This should every case the accepted chemical tests confirm the identifica- be provided Nith 16- and 4-mm. objectives, with a 2-mm. tion with tlie microscope, 80 that it seems reasonable to as- homogeneous immersion objective, if desired (although not sume that these characteristic appearances are constant and absolutely necessary), together with a 5 X and 10 X ocular. afford a reliable method of identification. Most of the vriter's work has been done with an 8-mm. o b jective and a 10 x ocular. This makes a very useful corn-. I Texlilc Wwld, 10, 2020 (1026),
Figure t2-Cuprammonium.
Figure 15-A
Viscose Type.
x
220
x
420
h'umeiaus specks and air-bubbles
FiCure 1s-A Typical Yisc0.e in Transv e r ~ eSectton. X 420
Fiaure 13-Chardonnet. X 440 Heavy Nick lines age deep gmeves
Figure i6-Rayon
Waste, Viscose Type.
x 220 PiLPr. damilped in reconditioning
Figure 19-A Typical Cupmmmonium In Transverse Section. X 480
hinntion for work on textile fibers, the magnification (200 X ) being quite sufficient to show all the structure clearly. The usual substage condcnser of the AbhC: type N. A. 1.20 is sufficient for all ordinary work. A polarizing outfit d l he found very valuable. The analyzer should be of the type that is placed immediately above the objective. An analyzing eyepiece, while very suitable for work on minerals or crystals where angles have to he read, is not so suitable for work on textile fibers on account of t.he small field. If the analyzer is placed directly above the objectim, a large and well-lighted field ail1 he obtained. The slight interference with the sharpness of the image caused thereby is of no material importance. Some form of measuring apparatus will be found very useful. The usual ruled disk ocular micrometer used with a 7.5 X ocular and calibrated with a stage micrometer rrill be quite as useful as the more expensive filar micrometer. Fibers which are to he rnettsured should he mounted in n
Figure 17-A
Typical Vlscnse Fiber. X 420
Figure 20-A Typical Chardonnet R w o n in Tran~YeS8FSecfion. X 440
