T H E JOURA’AL O F I N D U S T R I A L A N D ENGIA’EERIXG C H E M I S T R Y .
Sept., 1911
ABLE LE I --PASSIVITY.
BCBBLIKG TEST.
ProXI-eight. portional Steel Lost. k e a of steel. Pigment or base of Gram. 0.938 1 Aluminum paint. . . . 0 . 0 5 6 2 0.939 2 T a r cement paint. . . 0.0780 1.000 3 -1sphaltum paint. . . . 0.1000 0.921 4 Red l e a d , , . . . . . . . . . 0.1390 1.032 5 , Pitch p a i n t . , . . . . . . . 0 , 2 0 3 0.912 6 . Acheson graphite. . . . 0 ,222 1.000 7 , R . I. \V.paint. . . . . . 0 279 0.912 8. P. Sr B. p a i n t . . . . . . . 0.298 0.982 9. Slate lacqiier.. . . . . . . 0 . 3 5 5 0.904 LO. Cement paint. . . . . . . 0.4441 ’rAELI: JI.-p.ASSIVITY.
XVt lost per unit ax ea. 0.0598 0.0832
Relative inhibitive value.
0.:000
0.59s
O.l.510 0.i970 0 . ? 160 0.:!790 0 32iO 0 ,2650 0.491
0.396 0.302 0.277 0.214 0.155 0,16? 0.122
other of an insulation type like the one above described, are necessary to determine the efficiency of a paint. By carefully standardizing these tests it should be possible to compute the value of a paint in relation to some commonly accepted unit. By way of illustration, we may use red lead for one example and aniline pitch paint for the other. The problem is t o ascertain the relative efficiency of these two paints. Let “ I ” equal the inhibitive value of a paint and “ R ” the resistant or insulating value of the same paint, then “ V ” the total value of the paint equals “ R I . ” (An absolute standard to which to refer the inhibitive and insulating values of a paint must, of course, be eventually chosen.) In the case of red lead T’ = 0 . 2 8 2 X 0 , 3 9 6 = 0 . 1 1 2
1.000 0.71s
DAJIPFILXTEST, Pigment o r residue.
Order of efficiency
67 I
1 . . . . . . . . . . . . . . . . . . . . . . . . . Red lead P . S: B.paint Aluminum paint 3........................ Asphaltum paint 4. . . . . . . . . . . . . . . . . . . . . . . . T a r and cement paint 3. . . . . . . . . . . . . . . . . . . . . -4cheson graphite 6............. , . . . . . . . . . . . . . . . . . . . . . . . Slate lacquer
and for aniline pitch paint T’
0,473
x
0.302
= O.Ii+j,
TABLEIII.-INSULATIOS TESTS.
. *(
-
ti of coats.
pio.
Paint used.
2 1 R I . \\’. p a i n t . . .... 2 2. Pitchliianiline . . . . . . . . 2 3 Red lead (a).. . . . . 4. Red lead ( b ) . . . . . . 2 5 . Cementpaint . . . . . . . . . . 3 6 . Acheson’s graphite. . . . . 2 7 , P . & B. p a i n t . . . . . . 2 8. l s p h a l t u m paint. . 2 . 2 9. Whiteshellac . . . . . . . . . . 10. Slate lacquer.. . . 2 11, Aluminum paint. 2 12. Dull black var-lac., . . . . 2 Pitch d i p l . , . . . . . . . . . . . very thick 1
Amperage a t end of
2 -
f
Omin 10niin. 30min. 8 . 0 0.002 8.0 0.002 8 . 0 0.000 8 . 0 0.000
8.0 0.025 8 .O 0 . 0 S 8 . 0 0.020 5 . 0 0.025 8 . 0 0.000
8.0 0 . 0 1 0 8 . 0 0.085 5 . 0 0.120 8 .O 0 . 0 0 2
7
6 hrs. 24hrs. Omin.
0.013
0 . 0 4 0 0.0006
0,0693 0.1466 0.2456 0.3180 0,3756 0,5227 0.751 0.7695 1.1225 1.1569
0.010
0.010 0.015 0.015 0.028 0.054 0.075 0.130 0.120 0.180
..
0.020 0.020
..
..
INTERPRETATION O F RESULTS.
To obtain a comparative rating, the efficiency of some one paint was taken a t unity and all others calculated on t h a t basis. It is the opinion of the writers t h a t two accelerated tests, one of the inhibitive character described b y Cushmans and the
BfL
24 hrs.
1.00 . 0,473 0,282 0,218 0.185 0.131j . . 0.0923 o.ogoo . . 0,0615 4.8019 0 . 0 6 0 0,5273 0,8666 2.095 2.168 1.545 2.323
..
.. ..
. I
..
..
0,0130 0.0130
Efficiency = K/\V6. Assuming efficiency of R . I. IT-. = 1 . Wattage a t end of 6 hrs. = \Ve.
described b y Cushman.1 Table I gives numerical values from the bubbling test while Table I1 gives the relative efficiency of the paints as determined by the damp film test. A number of the paints were tested b y Magnussonx a n d Smith,’ in attempting t o find means t o prevent the corrosion of iron in concrete. While in these experiments, the conditions were different, the results in the main tend to confirm the same order of relative efficiency.
Bull. 35, Office of Public Roads, U. S. Department of Apriculture. A . I . E.E. Proceedings, 30, 939 (May, 1911).
0.012 0.040 0.090 0.045 0 . 0 9 0 0.065 0 . 0 7 0 0.088 0.100 0.130 0.130 0.130 0.140 0.200 0 . 2 0 0 0 . 2 1 0 0.210
30 min.
I hr.
0.0028 0.0073 0.0193 0.040 0.0006 0.0031 0.0091 0 . 0 2 6 6 0.005 0.115 0.00025 0.0021 0.0081 0 . 0 2 5 6 0.010 0 . 1 1 5 0.0002 0.0024 0 . 0 1 1 5 0.0450 0.042 0 . 0 6 0 0 . 0 0 4 5 0.0171 0.0411 0.1056 0.066 0.100 0.0094 0.0300 0.0652 0.1467 .. . . . 0.005 .. 0 . 1 0 1 0.231 0.15 . . . 0.0104 0.0463 0.1045 0.2295 0 . 1 0 0 0.150 . . . 0.00 0.0500 0.1325 0,3225 0 . 1 2 0 0.155 0 . 1 8 0 0.195 0.0126 0 . 0 5 5 4 0.1419 0.3369 . . . . . . . . 0.0183 0.0749 . . 0.155 0.185 .. 0 . 1 5 0 0.150 . . . . . . . . 0.0225 0.0773 . . .. 0.0025 0.0025 0.0020 0.0010 0.000 0 . 0 0 0 0.0002 0 . 0 0 5 5 0.0095 0,0110
0.008
I n order t o obtain other means for comparison, the same paints were tested by the accelerated tests
Cif.
2 hrs.
6 hrs.
.\lot comparable with others.
a LOG.
--7
2 hrs.
0.005 0.005 0.003 0.003 0.032 0.058 0.100 0.106
1 hr.
COMPARISON T E S T S .
2
..0 3
K a t t a g e a t end of
? -----_----
-.
8
j
.33
Then K = 0.0693.
comparative results which are consistent with service tests of a limited character. LABORATORY OF IXDUSTRIAL CHEMISTRS, UNIVERSITYOF WASHINGTOK.
-_____ A THERMOSTAT FOR MODERATE TEMPERATURES. B y -4. 11. BUSWELLAND RALPHH. ~ I c K E E . Received August 7, 191 1.
The ordinary thermoregulator consisting of a mercury interrupter and relay, operated a t low voltage, for turning on and off the heating system (electricity or gas), has given satisfaction. The other simpler type of thermoregulator, depending on the effect of temperature on a gas or a liquid, placed in a vessel whose only outlet is a J shaped tube filled with mercury and having platinum wires piercing each arm t o serve as binding posts for the electrical connections, is, in the forms previously used,I for a short time fairly satisfactory where a range of several degrees is allowable. But when it is desired t o keep a n in-
’
Summerville, Elec. W o r l d , 57, 112 (1911); cf. bibliography given by Geer, J . Phrs. Cizem.. 6, 101 (1902).
672
T H E J O U R N A L OF I N D U S T R I 4 L A N D E N G I N E E R I N G C H E M I S T R Y .
cubator constant to 1%-ellwithin one degree the following difficulties arise. I. When air is the expanding substance, the variation in atmospheric pressure, say 1.5 cm., will cause a change in volume of the gas of one in 50, whereas a t 37’ C., one degree will cause a variation of only one in 310; and the arcing, if the interrupter is used across a I I O volt circuit, volatilizes and oxidizes the mercury. 2.‘ When toluene or ethyl alcohol is the expanding substance, the arcing cracks the liquid, giving carbon and a gas in the case of toluene and a permanent gas (hydrogen?) in the case of alcohol. The production of gas in either case is so great when I I O volts are used t h a t the mercury is forced back and prevented from closing the circuit a t the desired temperature. The fact t h a t there is a critical arcing voltage, varying with the composition of the electrodes, below which no arc can be formed, suggested t h a t b y cutting down the voltage across which the interrupter operated the production of gas might be eliminated. Experiment soon showed t h a t with platinum and mercury electrodes operating across 2 0 volts or less, there was no arcing effect and practically no gas was formed b y the spark a t the make and break.
A thermostat (bacteria incubator) for water analysis, t o be kept a t 3 7 O b y a thermoregulator operated on this principle, was made, using a wooden box 14’’X 18’’ X 24”. Incandescent lights for heating were arrangedj(at the bottom a n d a sheet iron plate was placed above them t o give uniform distribution of heat and t o shade the cultures. The thermoregulator as shown in Fig I is easy of construction. A is a glass tube one centimeter in diameter, holding about 1 5 0 cc. of absolute alcohol. B is a capillary tube (inner diameter about 1.2 mm.) extending between the reservoirs C and C’. Mercury fills B and C’. A is connected t o C and D b y ordinary 6 mm. glass tubing. D is a stopcock for filling the apparatus. Nos. I , 2, 3, 4 and j are platinum wires
Sept., 1 9 1 1
which pierce the capillary tube B and are connected b y wires t o the ‘‘Nichrome” resistances I , 11, I11 and IV. The latter .are mounted on an asbestos board placed with the lights beneath the iron plate, and are so constructed that the drop in pressure across each is 2 0 volts. Lights E, F and G (one 8 c. p. and two 4 c. p. lights) are arranged in series with the mercury, and with a n eight candle power light H, connected t o burn at full heat continuously, give somewhat more than enough heat to keep the temperature a t 3 7 O C. The apparatus is so adjusted by the stopcock D t h a t a t 37’ the mercury just makes contact with wire No. 2. The circuit then contains resistance I and the mercury in series with the lights E, F and G. If the temperature rises slightly the mercury is forced down, the contact a t 2 is broken, and resistance I1 is thrown into the circuit. If i t continues to rise, I11 and I V are thrown in in like manner. If the temperature drops, the mercury rises cutting out the resistances and brings the lights up t o full heat. Without attention the incubator kept within half a degree of 3 7 O for two months. Reservoir C is large enough so that if the current is cut of€for any reason, mercury will not be drawn over into A, and C’ contains enough mercury so that under the same conditions the left arm of B will never be emptied below 5 . On turning on the current the incubator comes u p t o temperature without attention. The number of ohms for the resistances were deRf? termined by the formula r = -~ where r is the L - e’ resistance desired, R the resistance already in circuit, e the drop in voltage desired ( 2 0 volts in this case), and L the line voltage. I n our case where the resistance of E, F and G was I I O ohms, resistance I was 24.4 ohms, I1 29.9 ohms, I11 37.0 ohms and IV 45.5 ohms. These resistances were made of No. 3 2 Nichrome wire, two ohms resistance per foot. A convenient tool for making the resistance plates is shown in Fig. 2, in which M is a slit sawed in the
end through which the wire runs. The lower end is flattened so t h a t the tool may be held easily between the thumb and fingers. I t works equally well with ribbon or wire. The plates are as compact as those
T H E J O U R N A I , OF I N D U S T R l d L A N D E N G I N E E R I N G C H E M I S T R Y .
Sept., 1 9 1 1
of the same resist.ance wound in the old n-ay on brads driven in a board, and not more than one-third the time is required for winding. The network may be conveniently stayed by the use of a little asbestos cement. The glassblowing and bending is all of a simple character and can easily be done in three or four hours; and the winding of resistances and making' connections should require no longer time. ,
673
The temperature may be lowered by raising the apparatus above the source of heat. Electric lights, encased in compartments made of asbestos board, are used in this laboratory for heating the extraction flasks, but the apparatus described may be
USIVERSITY O F >rAlSE,
OROSO
[COXTRIBUTION
PROS1
?"E
CHEJIICAL
AGRICCLTURAI.
DEPARTMENT OF
THE
0SLAHO)l.L
EXPERIMENT STATION.]
A NEW FORM O F EXTRACTION APPARATUS. B Y C. K . F R A N C I S . Received July 15, 1911
The apparatus1 (Fig. I ) consists of a modified condenser, A, and an improved flask, B , together with a n extraction tube, C:. There are no ground joints, the one seal necessary being made with mercury. No support is required for the flask. The condenser used in the apparatus shown is of the Hopkins type, provided with a special extraction chamber, EC, and a dropping tube, DT.* The lower part of the extraction chamber is partially constricted on opposite sides about I O mm. above the bottom. The two constrictions are so made (Fig. 2 , I N ) that each extends nearly one-half the cricumference of the tube without meeting on either side. This arrangement leaves the internal diameter, 3 cm., unchanged in two diametrically opposite places and reduced t o about 2 . 7 cm. for the remainder of the circumference. The modifications of the Knorr flask are two knoblike perforated projections (Fig. 3. PP) ion opposite sides of the neck and about 1 5 mm. above the base of the shoulder. These projections are so placed that they fit into the extraction chamber where the internal diameter is greatest. The holes (Fig. 3, HO) in the neck of the flask are about 3 mm. in diameter. These permit ample passage for vapor and return for the liquid which would otherwise collect around the neck of the flask. The extraction tube (Fig. I , C) is 9 cm. long, 2 . 2 cm. external diameter and has a stem about 2 cm. long. It may be packed with cotton, asbestos, etc., together with the sample, and supported on the flask as shown in Fig. I . A spiral spring of copper wire laid crosswise and pushed down on the charge prevents the contents from being forced out of the tube by expansion of vapor. The regular paper shells may be used in place of glass tubes if supported on very small funnels. The flask may be locked into the condenser by inserting the neck into the extraction chamber and giving the flask ti quarter turn. This system fixes the flask securely and it cannot be accidentally pulled over or disturbed in any way. N o support for the flask is necessary; this is especially convenient when heating with electricity or with warm water. A modification of a piece of apparatus designed by G . L. Holter and which has been in use in this laboratory for several years. Any of the ordinars condensers mas be modified in the same way.
Fig. 1.
found convenient where there is waste steam or warm water available. The arrangement is economical in the use of solvents; 30 cc. of ether are ample for the usual f a t extractions.
