I10
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y .
the viscosity of oils with a n accuracy which is very great. The viscosity of about twenty fish oils was measured a t 30°, 5 o 0 17 0 ° , and g o o . 2 . Measurements of the viscosity of these oils were taken at 30°. They were heated t o 90°, cooled t o 3 0 ° , and the viscosity redetermined, and it was found t o be unaffected b y the heating. The separation of solid fats from the sand shark liver oil causes little change in its viscosity, perhaps because the viscosity of these fats is practically identical with t h a t of the oil.
I
Feb., 1912
3. The fluidities of the oils are not linear functions of the temperature, indicating t h a t there is some association a t the lower temperature. This theory is supported b y the fact t h a t esters have been shown t o be associated. The author wishes t o express his gratitude t o Mr. Adrian Thomas and Mr. William Crozier for aid during the course of this investigation. RICHMOND COLLEGE. RICHMOND, VA.
LABORATORY AND PLANT
I
I n the setting of hydraulic cements we have something much more complex, though we have been instructed b y the case of plaster and b y some of B y CHAS F. M C K E N N A . Received Jan. 10, 1912. the points of similarity in it. One cannot give a clear definition of the term Powdered Portland cement clinker is a complex “hardness” which will serve for all the meanings solid solution of silicates and aluminates high in in which it is used. The mineralogist using Moh’s lime. When i t is wet the alkaline lime solution Scale always means b y this a measure of resistance resulting reacts on the silicates, producing a colloidal t o scratching or abrading ; the wood-worker means mass. A thermal effect occurring here in the bethe resistance t o cutting; the steel-maker sometimes ginning is the absorption of heat due to solution or means b y i t the resistance t o deformation under the passage of the solid salts into the ionic condiapplied loads; in fact, indentation tests rule in many tion. fields rather than scratching, cutting, or any other I n the setting of cement the first gelatinous mass form of test. formed is less and less permeable, due t o drawing I n the case of hydraulic cements, the first stages away of water coincident with the lowering of temof hardening have been usually measured b y resist- perature; then as the crystal formation begins, the ance t o penetration; the later stages b y finding the proportion of free water momentarily increases again increase of cohesion determined b y resistance on and softens the colloids. Later, the full interlacing uniform cross-section t o tractive or compressive of crystals and the drying of the colloid admit less forces gradually applied until rupture occurs. a n d less of penetration, and thus we have the deThe setting of plasters and cements is the very velopment and finally the end of the process of setfirst stiffening and rapid development of cohesion ting. u p t o the stage where needle points under moderate Hardening can then go on through further mopressures do not penetrate the surface, or where lecular interchanges leading up t o the formation small test objects are easily handled without frac- of silicates of lime and alumina analogous t o some ture. Beyond this t h e phenomenon in which the of the hydrous silicates of mineralogy. cohesion due to complex mineral-forming reactions According t o Michaelis, the exact steps are described is step b y step increased until a considerable age is as practically a migration of water throughout t h e reached is called the hardening. mass. The first particles of clinker are dissolved The chemical phenomena occurring in the setting on the surface ; the supersaturated lime solution of plaster of Paris are chiefly those due t o the energy thus formed reacts t o form a gelatinous mass, a n d in supersaturated solutions. Where a small pro- when crystals of aluminate of lime are formed t h e portion of water is used a hydrated sulphate of lime water separated goes further t o attack newer parof one form goes into solution and the concentration ticles of the clinker nodule, later deserting the colcauses the settling out or solidification of another loids formed and passing into the air or into t h e form of hydrated sulphate; the water released from water in which i t is immersed. this helps t o dissolve more again of the first form, These reactions are complicated again b y t h e which, b y concentration, duly deposits again, and presence of sulphate of lime, which serves t o form thus the process is continuous t o total solidification. with the aluminates of lime a double compound of Similar phenomena can be observed in super-satuslow-setting qualities, neutralizing the usual effect rated solutions of some salts, which can be caused in a cement rich in aluminates of lime, where t h e t o deposit crystals and thicken almost t o total solidisetting is very quick and the development of heat fication. The setting of such a compound of hysudden and great. Thus you will observe we condrated sulphate of lime is rapid, and except for effects sider setting t o be consequential upon the formation of drying, the maximumx hardness is obtained a very of both colloids and crystalloids, few hours d t e r the .gauging. Apparatus for observing these changes in the set1 PaDer at the Fourth Annual Meeting, American Institute of - Dresented . tinp Drocess have usuallv been simple. For expert. Chemical Engineers, Washington, December 20, 1911. HARDNESS OF PLASTERS AND CEMENTS, AND A SIMPLE CHRONOGRAPHIC APPARATUS FOR RECORDING SET.’
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A
Feb., 1 9 1 2
T H E J O l J R N A L OF I i V D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y .
workers i t suffices t o use the thumb-nail. With skill and accustomed observation they thus obtain a definition which is as remarkable as the means are simple. Nothing has been developed towards providing means for observing set in plaster of Paris; the contraction and dilation, however, have been observed by van’t Hoff in a beautifully simple apparatus. General Gilmore recommended, for observing set in Portland cement, a weighted coarse wire and a more heavily weighted fine wire (Fig. I ) for the determination, respectively, of the first stiffening (initial set), and the firm resistance to any penetra-
Fig 1
tion or deformation (final set). Neither of these methods are instrumental or fitted t o record distinct differences. The first apparatus designed for such a purpose was t h a t of Vicat, the French chemist and authority on cements. The Vicat needle (Fig. 2 ) is a weighted one, cylindrical and I square millimeter in area on the face, moving in a vertical scaled-off guide and falling upon the mass of gauged cement in a mold
the time when there will be no mark upon the surface from the needle. However, chronographic and automatic apparatus have been sought for. Professor A. Martens, of Charlottenburg, designed an apparatus in which needles energized by magnets are dropped and raised again as a clock movement makes the contacts. The Amsler-Laffon cement setting recorder (Fig. 3) has been used in Europe. This is described in the journal “ Cement, ” from which the accompanying figure is taken, and the following description: In testing the activity of cements by this apparatus two molds are filled with a plastic paste and two needles are lowered upon the cement a t certain intervals, penetrating more or less into the mortar according t o the progress of setting. The depth to which each needle enters the mortars is recorded on a drum b y two separate pencils. After each strike of the needles the drum turns a little and the table on which the molds rest advances a step from right to left. The needle-holders are lowered and raised b y a lever, which is set in motion b y a spiral spring; a clock movement lets loose a governor and stops it again when the strike of the lever is completed. The diameter of the needles is one millimeter. The weight of each needle-holder is 300 grams. The Nicol Spissograph (Fig, 4 ) , the invention of R. Gordon Nicol, of Aberdeen, Scotland, and made b y A. and J. Smith, of that city, is similarly designed. This apparatus consists of a clockwork which raises and lowers, every three minutes, a pointed needle; a t the same time the paste is rotated in a spiral t o present a different spot to the needle a t every contact. On the apparatus is a thermograph recording on the same chart the temperature of the air a t the time the test is made. The whole is covered with a glass case, and arrangements are made for keeping the temperature and humidity regular. One of the best achievements in this line has been Gary’s apparatus and the resulting investigations. He used the thermal changes during setting as the basis of study, and b y photographing the changes of the mercury columns secured data for a chart (Fig.’5 ) . Such a record as was thus secured gives admirable indications of the energy a t work. None of these automatic instruments has been used in this country as far as I know. The following is a n extract from the official report of R. Feret, Boulogne-sur-Mer, a t the Fifth Congress of the International Society for Testing Materials, held a t Copenhagen in 1909: “
Fig. 2
below. The initial set is taken as the time a t which the needle will not penetrate within a certain distance of the bottom of the mass, and final set as 2.ghys. Chem., 7 0 ,
146
I11
DURATION OF SETTING.
”
“ T h e use of the Vicat needle continues to be the only practical method in use for the determination of the duration of the period of setting of hydraulic cements. The appliance is of extreme simplicity, but its readings are sometimes uncertain, especially when i t is a question of determining the end of the period; besides, the readings are of a purely con-
ventional character and do not appear always to bear a sufiiciently constant relation to the duration of the setting period of the mortars of actual prac.
Pic. 3 .
tice. The discovery of more exact methods has therefore been attempted. Methods of testing based on the measured variations in the electric resistance of mortars while hardening have not given results oi interest, “Other investigations have aimed at the definition of the setting by the determination of the temperature of the mortar during its continuance. Reasonably regular curves were obtained by this method. which, however, were dependent on the testing conditions and corsesponded with chemical phenomena, the relation of which t o the change of consistency called setting has not yet been quite clearly established. “The principal nature of the method t o be employed may be the ascertainment of the time, reckoned from the consmencement of thc gauging, during which a given mortar can, with impunity, be furthcr used witliqrit having to he revivcd by a fresh addition of water or a too violent . ,. , ‘8; ., mechanical treatment.” ’ Reading this I was led to take up again certain studies of setting which I had made some years before, in which I was observing the resistance t o penetration b y glass rods, and the resistance t o withdrawal of glass threads progreisivFly acted upon b y the salts and compounds forrncd in the paste and operating during t h e setting process. I thought that the holding power of newly formed salts upon glass might be progressively observed. Also it seemed to me then that the testing of
the surface b y wire points 61mwed a lack of cffectivcness in setermining set in c(~lloidsand crystallo-colloidal binding agents. Penctr;ition.along aplane similar to shcnr bya knifehiadc should give better results than mere resistance t o rupture of i~ suri;ice at m c point, just as the cutting of metalbya turning tool aiiords a better test of cohesion than indentation or scratching does. If sevcral glass rods or pins, ten or iifteenthousanclths of an inch in diameter, are driven into soit 1,aste of plaster or cement, and a t intervals are tipped forward. they will cut the mass at first considerably; later t o a diminishing extent ; anil finally\nhcn thc colloids and crystals arc hoth well formed about the pins (a period corresponding with the final set or resistance to tile light wire heavily loaded) they snap off sharply and suddenly. Such acomhination seemed to give indications of very fine anil measurahlc (iiflerencc?,. K’ONil you were t o briiic ui) azainst a linc o f such
Feb.,
26
1912
T H E J O U R N A L OF I , Y D I r S T R I A L A N D E-VGISEERIi'\'G C H E M I S T R Y .
I
/-
Fig 5 .
I have made many models of apparatus for such a purpose by making simple adaptations of things at hand till the present model developed and p u t lately into this final form by hfessrs. Schneider B ~ ~of ~Jersey , , Cit,+,, the gifted mechanicians who are known all Over the world for the simplicity and beauty of their work on scientific instruments, I will explain in as few words as I can the operation of this instrument (Fig. 6). It .consists of a screw, H, operated 1317 clockwork, giving tw13 speeds, there being a shifting lever, L, for a speed of one inch a n hour and another speed of double that. I t can also be operated by hand through a knurled head a t one end. This screw, H, carries a moving finger, F, projecting over a long rectangular paste mould, C. This moves forward and strikes successively the glass pins P inserted deeply into the paste and projecting vertically from i t in one line. As each glass pin bends forward it bears against a smoked glass rod and traces its path until, when a distinct resistance is attained, it snaps off. Back of this is an adjusting frame to carry the glass rod, and this can be brought forward very delicately, or drawn back, by the aid of a fine adjusting screw, A, at the back. A metal mold is filled with freshly gauged cement and run into place between the screw and $he adjusting frame. The glass rod, which
113
has been previously smoked and then rubbed clean over one-half of its surface, is inserted in the frame and brought forward over the center of the paste so that against the clean part of its surface these little pins are guided by it as they are inserted. So far as my investigations have gone I find that fifteen one-thousandths of an inch (0.015) give strength enough for meeting resistance and a t the same time giving a tendency to snap. They are pushed in vertically along the middle line one-half inch apart; the glass rod is drawn back by the screw A and the untouched smoked part is turned over so that it can be brought up against the pins by the screw again, ready for any record. Then the clock is started, the finger begins t o move, and as it strikes each pin successively it makes the respective record of the resistance to penetration a t that point and time. A maximum and minimum thermometer can be attached to the base plate. When everything is thus arranged the top glass case, can be put over i t , leaving a small dish of water in the case, and the whole may be left for instance over night. In the morning the entire record is on the glass rod. Records thus made resemble the markings in Fig. 7 . (The record given for plaster of Paris is not symmetrical as t o time, as the legend shows.) These glass rods, with the records upon them, can be varnished and preserved for examination at any time, or the record can be photographed on sensitive paper and thus preserved. From plaster of Paris I obtained a simple record of differences in resistance to penetration. I have not had many opportunities to experiment with varieties of this substance, but I expect to find that the instrument will readily indicate the differences due t o changes in percentages of water, catalytic From Portland cement the first few records already obtained are most interesting. It seems that in every normal Portland cement I have thus tested
Fig. 6 .
T H E JOL-RA-AL OF I A Y D I ; S T R I A 4 LA,\-D
114
ESGI:\-EERIAYG C H E M I S T R Y .
Feb., 1912
NORMAL PORTLAND
3
6
9HRS
3
6
9HRS.
DO
12.18
12.19
12.20
TOTAL
12.21
3 MINUTES PLASTER
10.45
10.48
10.49
10.50
10.51
1054
DO
11.15
II.
OF
PARIS
30 M I N U T E S T O T A L
Fig 7
there is observable in or about the third hour an indication of a relaxation of the stiffness first obtained and then a resumption of hardening. Comparing these results with those of Gary’s thermal studies, it is seen t h a t he observed a marked lowering of temperature a t or about the third hour. If we consider again the most modern theories of setting, I think we can explain this. The cooling effect of course is a t the period when salts are going into solution most rapidly. I t is well known that if a break occurs in a temperature-solubility curve which is otherwise continuous, i t is a proof that the solid substance which is in equilibrium with the solution, has passed into another form a t the temperature of the break. We have the reverse of this in our record of cohesion, namely, t h a t the break in continuity of the marks of increasing cohesion indicates the separating out from a saturated solution of a greater proportion of still another component, and that the water thus freed permeates the colloid and softens it. Later by desiccation, b y absorption of the water within and further crystallization, cohesion begins to increase and impenetrability and hardness go on. The discovery of this slack period or reverse set explains contradictions experienced in the past in measuring or determining the initial set b y the surface penetration system. It probably also will explain anomalies occurring in the practical use of cement during the first hours of gauging fresh cement. If this observation of change in the order of setting should prove to be universal for cements with the sulphate of lime additament, we may have t o observe first initial set, then reverse set, and lastly final set, and distinguish between them in time and character. I t is my intention to continue work as opportunity presents on this instrument, which appears to be simple and useful, and in time we may hope t o reach a little further in our knowledge of the setting of plasters and cements.
bag and catching the solid matter in the bag while the filtrate is caught in a receptacle below. This method was conceived in the kitchen and has been used by house-wives for generations. Although it seems primitive, i t is the method a t present employed in most cane-sugar refineries. The great disadvantage of bag-filtration is that the bags have t o be turned inside out to be cleaned. The method of filtering through bags inwardly, that is, passing the liquid from the outside of the bag and draining the filtrate from the interior, has also been employed in sugar-house work to a limited extent. By this method the solids are deposited on the outside of the bag, and it is, therefore, more easily cleaned. I n this type the usual arrangement is t o enclose a corrugated plate or grid in the flattened bag to prevent it collapsing under external pressure, and a series of bags so arranged is enclosed in a box capable of sustaining a moderate pressure. A flat filter-bag provided with means to prevent i t from collapsing when subjected t o external pressure, and having a suitable drainage outlet for filtered liquor, constitutes a filter-leaf. The different methods b y which filter-leaves may be constructed are too numerous t o be described in detail here. The first large leaf-filter installations were introduced in the cyanide process, and were of the vacuum type. I n the vacuum leaf-filter the leaves are arranged in groups and submerged in the liquid t o be filtered, and suction applied to the interior of the leaves. The partial vacuum formed draws the filtrate into the leaves, whence i t drains to the vacuum receiver, or in the absence of a receiver i t is drawn directly through the vacuum pump. Vacuum leaf-filters are divided into two classes, namely, the movable leaf type and the stationary leaf type. In the former (Fig. I ) the “cake” of residue is first deposited on the surface of the leaf
LABORATORY OF CHAS.F. MCKENNA, NEW YORK.December, 1 9 1 1 .
RECENT IMPROVEMENTS IN FILTRATION METHODS.’ B y ERNSTJ. SWEETLAND. Received Jan. 6 , 1912.
Probably the simplest method of filtration is that of pouring the liquid t o be filtered into a suspended 1 Presented at the meeting of the American Chemical Society, New York, January 5 , 1912.
Fig. 1
