MOLECULAR ATTRACTION. XV. SPECIFIC HEATS O F T H E ELEMENTS AND SOME ENERGY CHANGES BY J.
E. MILLS
Part I1 In the previous article values for the specific heat of the elements obtained after a careful collection and critical examination of the data were given, and also certain other tables and data to which references will be made in this article. Diagram I below gives the atomic specific heats up to 1000' K plotted against the temperature of some of the elements for which the data are most accurate at low tempera-
Diagram
I
tures. Some uncertainty attaches to the curve for silver a t high temperatures. The unusually rapid rise in the specific heat of aluminum as its melting point is approached only
624
J . E. LVills
partly shown in the diagram is not entirely exceptional, but so rapid a rise is not certainly established. For mercury and nitrogen the atomic specific heats as solid, liquid, and gas a t constant volume are shown. The general trend of the curves is apparent to the eye and need not be discussed. That the curves approach zero a t the absolute zero, seems obvious. The total heat required to raise a gram atomic weight of the element to any given temperature is represented by the area bounded by the curve, the ordinate a t the temperature in question, and the abscissa. That only a very small error can be introduced into the total heat by extrapolating the curves to the absolute zero is apparent. If the law of Dulong and Petit were exactly true as originally proposed all of the curves should be represented by a straight line parallel to the temperature axis a t 6 . 2j , That boron, carbon, and silicon were exceptions was soon recognized. It was then supposed that a t high temperatures the curves for these elements would approach the value 6.25. This is indeed probably true, but with rise in temperature the atomic heat of all of the other elements also continues to increase. The curves shown on the diagram are quite representative, and a t no temperature do the atomic specific heat curves coincide, or even nearly so (except at the absolute zero). If the monatomic metallic elements alone are considered there is no real coincidence of the atomic heat curves at any temperature. T h e lines f o r most such monatomic metallic elements do roughly coneerge at about room tevtzperature. At o o C , for instance, the average value for the atomic specific heat of 26 such monatomic elements is 6.07 and at 50' is 6.28, but the actual values for the same elements range between 5.41 and 6.76 a t o o and 5 . 6 6 and 7 . 3 3 a t j o o C. Boron, glucinum, and titanium, whose molecular condition is not certainly known, give values greatly below the average values above stated, as do carbon and silicon, while arsenic, antimony, and bismuth, which have polyatomic molecules, are in fair agreement with the averages given. I n short,
ilolecular Attractiofi.
XV
625
at room temperature, considering the elements for which the best measurements exist, 30 elements show a range in the constant of Dulong and Petit’s “law” of about 2 5 percent and seven other elements show greater divergence. At all other temperatures the disagreement is worse. The essential facts have been pointed out before, but everybody has been brought up to love the “law” from childhood. The equation of Debeye gives the best reproduction of the specific heat lines of the solid elements of any equation yet proposed. The equation is highly complicated, its accuracy is still under investigation, and the correctness of the theoretical basis for the equation is doubtful. Nothing could be gained by its discussion here. In Table I the elements are arranged in groups and a number of relations are shown. T h e total energy added to a monatomic element jrow. o o absolute to its meltiiag point, i i d u d i n g the heal o j jusion,divided by the absolute temperature OJ the melting poifit i s nearly the same as the speci$c heat o j the liquid element at its melting point. (See Table I , columns headed “Heat a t melting point,” “Liquid” and “Average.”) The importance of this observation lies in the fact that it shows that the heat ojjusion i s merely supplen4entary to the speci$c heat o j the solid and that one could extrapolate the liquid condition to the absolute zero without great error so far as the energy content of the liquid is concerned. Thus the heat of fusion of sodium is fairly closely represented by the area (see Diagram I ) bounded by the specific heat curve of sodium, the ordinate axis, and a line drawn parallel to the temperature axis through the specific heat of liquid sodium. The specific heat of the liquid is in many cases very uncertain and due allowance must be made for this uncertainty. The specific heat of the solid element at its melting point is also given, and it will be seen that i t is usually oidy slightly Less than the specific heat of the liquid. Perhaps the above relation also holds for the polyatomic elements and for compounds when a correction has been made to allow for certain other energy changes involved.
626
J . E. Mills
0 0 0 0 0 3 0 0 0 0 0 0 0
B $ 3
0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
Molecular Attraction.
XV
627
The total heat in a gram atomic weight of the liquid element a t its melting point divided by the absolute temperature of the melting point is shown in Table I under the heading “Average gram atom.” The value for lithium so obtained is below 5.96, apparently therefore an impossible value as will appear more clearly later. The data for lithium were widely divergent and the values adopted are almost certainly wrong. The average values given apparently increase with rise in the melting point and the value for tin is therefore out of line. The change in the allotropic form of iron with rise in temperature accounts partly for the high value there obtained. The average for the polyatomic elements a t the melting point is apparently not so simple a function, but hydrogen and phosphorus are suspiciously out of line with what might be expected. The ratio of the total heat in a gram atom of the liquid element a t its melting point to the heat of fusion is given in Table
under the heading
“Total”
Again lithium, tin, Lf . phosphorus and hydrogen are suspiciously out of line. ‘‘WLf)’ The next column, under the heading 7, contains the atomic heat of fusion divided by the absolute temperature of fusion. Again lithium, tin, phosphorus, and hydrogen are out of line. The value given by gallium seems high and that for lead low. It should be noticed that Roos adopts 6 . 3 7 calories per gram for the heat of fusion of lead and this WLf = 2 . 1 9 . value would make T I
Next under the heading
___
WZU
T is given the quotient ob-
tained by dividing the total atomic specific heat in the soZid element at its melting point by the absolute temperature. Compare with Laemmeli’s statement “Die integral Mittel der Atomwarmen der Elemente im festen Zustand sind gleich, und zwar ca. 6.5.” The sum of the values in this column and those in the previous column equal the average per gram atom at the melting point already given. Lithium is out of line, and while several of the other values may be, they are
J. E. Mills
62 8
not strikingly wrong, indicating that it is probably the heats of fusion of tin, lead, phosphorus, hydrogen (and gallium and lithium also) that are either wrong or somewhat exceptional. The value of the heat of fusion of tin has often been determined and is probably correct. The other values mentioned should be investigated very carefully. T h e values shown in this column are of particular interest because they are seldom m u c h greater than 5 . 9 6 awd iwdicate that those theories based u p o n the su$qosihm that metallic electrons require notable s$eci$c heat eNergy are wrol.zg. T h e atomic speci$c heat often greatly exceeds j .96 as the tables given in Part I have shown, but the elewent probably always melts before the average energy from o o absolute per atom at comtant d a m e equals this amount. I n the next to the last column of Table I , under the heading “Total - 2EK,”is given the difference between the total energy in a gram atomic weight of the liquid a t its melting point and twice the kinetic energy of the substance a t the same temperature, the kinetic energy EK being calculated from the equation
eK=
RT w
calories per gram. nz I n making this calculation for the polyatomic elements the following formulas were assumed: Hz, On, N n , Sz,C12, Br2, 12, Pq, Sbz, Bin. Consequently the values n a y be greatly wrong €or sulphur, antimony, and bismuth, and possibly have no great significance for the polyatomic elements. A better method of determining and comparing the effect of the attractive forces is shown later. This difference, Total - zEK, should not be negative. For the nionatomic elements this difference is probably a fairly accurate measure of the energy required for expansion against the attractive forces throughout the interval o O absoc lute to the melting point. It will be noticed that some of the columns in Table I contain some very suggestive regularities. Just how far the irregularities may be due to the data used it is not possible to say and speculation would seem useless. My hope has I
3//z
__ =
iVolecular Attraction. X V
629
been that a discussion of all of the available data would so eliminate gross errors that a rational theory of the specific heat energy would become possible and I trust t h a t this paper will prove that this hope is at least partially fulfilled. “mLV” I n the last column of Table I , under the heading is shown the atomic heat of vaporization divided by the absolute temperature. The zero group gives values as follows: helium 4 . 6 5 , argon 1 7 . 7 , krypton 18.8, xenon 1 8 . 9 , and niton 1 9 . 6 . Also carbon = 3 7 . 3 . Part 111 The energy added to a substance as its temperature is raised can be conveniently considered as energy spent in: I . Overcoming the external pressure = B E . 2 . Increasing the kinetic translational motion of the molecule = E K . 3. Overcoming the attraction between the molecules = E,. 4. Increasing the internal motion of the atoms within the molecules = EI. j . Overcoming the chemical attraction between the atoms = E,. The total added energy is therefore B E EK E,
E1
+
+
+
+(I)E,.The energy spent per gram in overcoming the external
pressure can be calculated from the equation E* = 0.0431833 P(V - v) calories, 2. where the pressure is given in millimeters of mercury per square centimeter, and V and ‘LI denote the volumes of a gram of the substance after and before expansion. For solids and liquids the change in volume on expansion is so small that I& can be considered zero for them. (2) The energy spent per gram in increasing the translational motion of the molecules for a perfect gas is given by the equation I.
EK
RT
=3/2-=----
2*9791Tcalories,
m m already given. The fact that a dissolved non-electrolyte in
J . E . Mills
630
dilute solution exerted the same pressure as osmotic pressure as would be exerted by the molecules of a perfect gas under the same conditions led the author and others to argue that the translational motion, and hence the kinetic energy, must be the same in the liquid as in the gaseous condition a t the same temperature. This idea is, however, wrong. It seems likely that in the liquid condition, and therefore probably in the solid condition, the substance retains, due to the effect of the attractive forces, twice the kinetic energy that the same substance will retain as a gas under the same pressure and at the same temperature. Somewhat different explanations are given. The author's idea is founded upon the fact that centrally acting attractive forces under the inverse square law necessitate that 70, particles in stable kinetic equilibrium retain as much kinetic orbital energy as they give out, if temperature energy is zero. See the original papers.l The retained orbital energy per gram E, can be calculated from the equation
E,
3.
= pf
3dd calories,
where p f is a constant for each substance calculated as shown later, and d is the density of the substance. When the temperature is not zero the retained orbital energy is in the liquid 2 The temperature energy is EK. condition, ~ ' ~ 4 EK. Hence, on lowering the temperature ~ E isKgiven out. Or the following statement might be considered more clear by some. When n particles are in stable kinetic equilibrium under the action of central forces varying as the inverse square of the distance between the particles, the effect of increased temperature is to increase the major semi-axis of the orbits of the particles. Such increase requires the absorption of energy equivalent to the increase of kinetic temperature energy added. It is possible to increase the major semi-axis without altering the volume. If the volume is altered a greater addi-
+
1
Phil. Mag.,
22, 84 (1911); Jour.
Phys. Chem., 19,657 (1915).
Molecular Attraction. X V
63 1
tion of energy than 2EK is required, but this additional energy required to change the volume is rightly considered energy of expansion and is classed under E,. The second explanation is essentially the same as the first, b u t involves an assumption as to the nature of the orbit-an assumption, however, that I believe is justified and necessitated by ordinary mechanical laws. Hence for a substance in the liquid condition we have per gram 4.
( 3 ) In the series of papers to which this article belongs I
have shown that the following equation holds true: 5.
where L is the heat of vaporization per gram, EE is the energy spent in overcoming the external pressure during the vaporization, d and D are the densities of liquid and vapor, respectively, and ,ut is a constant for any particular substance. Abundant evidence of the truth of the equation has been published. The equation was theoretically derived upon the assumption that the force of attraction varied directly as a constant and inversely as the square of the distance apart of the attracting particles. This theory would indicate that the energy required per gram to overcome molecular attraction during any given expansion could be obtained from the expression 6. E, = p' (34&- 34&)calories, where dl and dz are the densities of the substance before and after expansion. It has not hitherto been possible to prove the truth of Equation 6 outside of the saturated vapor-liquid region for which Equation 5 was proved true. I will here assume its truth and proceed to see if the facts warrant the assumption.
J . E. Mills
632
(4) The well-known theory of Waterston gives the rela-
tion 7.
for a perfect gas. Solving for
E1 = R 7 5-3Y . G .
8.
Putting R = 9.
EI we get
2 / 3 Ewe ~ have E1 =
1.666 - y 7-1
.EK.
Therefore for a perfect gas the energy which goes inside the molecule is proportional to the kinetic energy of the gas and can be calculated when y has been measured. For .a monatomic gas GI is always zero, y being equal to I , 66, a relation which holds for the monatomic gases over all regions in which they have been investigated. For polyatomic gases the relation is much more complex. Theory based upon the equipartition of energy-a theory upon which there is not unanimous agreement-indicates that E, = nR - = *m calories per gram, IO. 2m
m
where H, is the number of atoms in the molecule. Hence the molecular specific heat at constant volume for a diatomic gas would be 4.96 and for a triatomic gas 5.96. For several of the most stable gases the actual value usually obtained is less than the value assigned above, but it must be remembered that the specific heat a t constant volume varies with the volume, that is, with the pressure, to which the gas is subjected. It would seem probable that a pressure could always be chosen a t which the molecular specific heat at constant volume would equal the assigned values and that the slight variations could be explained as a secondary variation due to the attractive forces, were it not for the recent experiments of Eucken with hydrogen a t very low temperatures. Eucken finds that a t such temperatures the hydrogen molecule be-
IVolecular Attractiow. X V
633
haves as a molecule of a monatomic gas. Further discussion can well await the substantiation of Eucken’s results. ( 5 ) For all polyatomic gases the specific heat a t constant volume increases with the temperature until the molecule is broken down into its atoms. Since a part of the heat absorbed results finally in the decomposition of the molecule this part can be regarded as chemical energy going t o overcome the attraction between the atoms of which the molecules are composed. The heat so absorbed seems to increase as the temperature of decomposition is approached and to approach zero with extremely stable molecules a t low temperatures. GI as calculated from Equation g will usually, therefore, contain some energy which should be classified as E,. It is not yet possible to rely with confidence upon the truth of Equation IO, and there is as yet no method for calculating theoretically the chemical energy absorbed. I n view of the above facts our present knowledge can be expressed as follows: For a monatomic gas or liquid, E1 = o and E, = 0. nR For a polyatomic gas EI is probably equal to (remembering that substantiation of Eucken’s results may revise this conclusion) and E, = 0 , if the molecule is extremely stable, and E,>o for less stable molecules, and gradually increases until the molecule decomposes. I do not contend for the idea that chemical and molecular forces are necessarily different in their ultimate nature, but the distinction between atoms and molecules and therefore between E, and E, made in the foregoing discussion needs no defense here. If the views above outlined are correct the total energy in a gram atomic weight of a liquid monatomic molecule a t its melting point can be calculated with only slight error, as follows : 11.
Total energy =
~ E 4-K E,
+-
= ~ ~ T9 6 ~ v z p ’ ( ~ 4d ~ 34dM.p.) calories,
J . E. Mills
634
IR -?
N
Y
3
k
a
$ Q. I
0
0
0
0
0
0
0
0
~
0
~
0
0 0 0 0 0 0 0 0 0 0 0 0 0
0
0
Molecular Attraction.
XV
635
where do is the density of the element a t the absolute zero and d, p. is the density a t the melting point. Before making this calculation it is necessary to calculate p’. This calculation is made as shown by Equation 5 , the necessary data and the results being shown in Table 2 . The data not given in Part I of this paper have been for the most part obtained from Landolt, Bornstein and Roth’s “Tabellen” and the “Tables Annuelles.” The values for the density of the vapor a t the boiling point have been calculated from the equation 12.
The values of the density a t o o absolute given in Table 3 have been obtained by extrapolation either by myself or by
others. The values of the density of the liquid a t the melting point there given are from the tables cited. Using these values and the values of p’ given in Table 2 , there are shown E, the results of the in Table 3 under the heading zEK calculation of the total energy in a gram atomic weight of the liquid a t its melting point as given by Equation I I . The observed values are given under the heading “Observed.” The agreement between the calculated and the observed values for mercury, aluminum, tin and lead are quite as good as could be expected from the accuracy of the data a t hand. For copper and zinc the divergence between the calculated and observed values is too great to be attributed to errors in the data without further experimental investigation. Therefore no final conclusion as to the correctness of the theory can be drawn, but the fact that substantial agreement is reached for four of the six metals for which the calculation was possible warrants a further extension of the theory. Fortunately this is possible in several ways, as shown below, and the results obtained, as will be seen, are such as to greatly strengthen belief in the substantial accuracy of the ideas advanced. To test the idea advanced further we proceed next t o calculate the total energy in the vapor of mercury at its boiling
+
J . E . Mills
E 0
.A
a
2
.3
x
8
Molecular Attraction. X V
63 7
point, again making use of Equation 1 1 and substituting the density of the vapor a t the boiling point for the density of the liquid at its melting point and adding the energy required t o perform external work during the expansion. The data have already been given. The equation takes the form 14.Total energy in one gram atomic weight of mercury - a t its boiling point = 2EK E, E* = 3 R T mp'vapor ( 3 d d o- ' d d G . ) 0.0431833 P(V--) = 3,752 12,926 -I1,252 = 17,930 calories. The above value is t o be compared with the observed value of the total heat of a gram atomic weight of mercury vapor obtained from data previously given. Thus we have for energy added as
+
+ +
Specific heat of solid Heat of fusion Specific heat of liquid Heat of vaporization
=
Total
= 18,047 calories
+
+
1,2j 4
calories 559 calories = 2,634 calories = 13,600 calories =
The agreement between the calculated and the observed value is certainly excellent. As is well known, the specific heat of mercury vapor appears to be exactly in accord with theory and hence the above simple explanation of the total heat in the vapor is of great theoretical interest. It is well to point out that Equation 14is subject to three slight errors. First. The molecules of solid mercury are probably not exactly uniformly distributed throughout the space they occupy. Second. The vapor pressure of mercury has a slight effect for which no allowance is made. T h i r d . The attractive forces between the molecules of mercury vapor possibly introduce another error. The ideas advanced enable the specific heat of liquid mercury to be calculated. The result of such an attempt is shown in Table 4. The calculation is again based on Equation 1 1 and the energy of attraction E, is calculated from the change in density as before. Thus, 15. Specific heat of monatomic liquid = 2EK E, =
+
J . E . Mills
N
m N
?
0
I
0
0
0
U
0
0
Mole Fular Attraction. X V
63 9
where dl and dz are the densities of liquid mercury a t the temperatures tl and tz chosen a t equal temperature intervals below and above the temperature for which the specific heat is desired. The observed specific heat of liquid mercury given in Part I of this paper is shown in Table 4 for comparison with the calculated values. The agreement is probably not quite within the limit of experimental error of the data but is sufficiently close to confirm the general accuracy of the ideas advanced, as the slight divergences shown may be due t o some of the sources of error mentioned in the preceding paragraph. It should be pointed out that the reciprocals of the distances apart of the molecules of liquid mercury between the temperatures -20 and 360 C decrease almost exactly linearly with the temperature. The author has heretofore published no proof that the inverse square law of molecular attraction could be extended beyond the saturated vapor liquid region for which the fundamental Equation 5 has been proved true.l T h e calculations above made are evidence that the inverse square law o j attraction holds true to the absolute zero both for liquid and solid. A density temperature diagram is shown for isopentane in Diagram 2 . The relations there shown while not exact (the lines dod3d4 and d5dcd4 are not exactly straight and do
Diagram z 1
See series of articles in this Journal.
Also Phil. Mag., Oct., 1910;July,
1911;Oct., 1912;Jour. Am. Chem. SOC.,31, 1099 (1909).
J . E. Mills
640
not meet the temperature axis exactly a t twice the criticaf temperature) seem to be approximately true for all substances, The ideas advanced indicate that the energy, exclusive of energy going to do external work, necessary to be added to change a monatomic element, From do t o d, = p’3d& since density at d, = 0. ‘I
“ ‘I ‘I
d, tods = €$K do t o d7 = 2 I 3 ~ d7 to dl = ~ ’ ( ~ 434TJ & -since d 7 = do di t o dz = , u ’ ( ~ ~c J34i5) ~ dz to de = x
Starting with a monatomic element at the absolute zero and with a density d o it can theoretically be changed to a density dz a t a temperature T along the path dod7dldz or along the path dod,d6dz, and the energy necessary to be added must be the same along either path. Therefore we have 16.
+
~ ’ ~ . \ i &EK-x
=
+
+
ZEIC ~ ’ ( ~ d & -3d&) -,u’(~.\~Z--~~Q = ,u’~~&-GEK,
whence x
where x is the energy necessary to change from the condition of saturated vapor a t the temperature T to the condition of a gas at the same temperature whose molecules are theoretically at an infinite distance apart and hence in the condition of a perfect gas. This result is being further investigated. It is not possible to test the value for x given above directly from existing specific heat data. But evidence that the argument given is in accord with the facts is obtained by calculating the total energy required to raise a gram molecule of some stable diatomic gases from oo absolute to o o C and comparing the calculated values with the observed. The calculation is made on the supposition that no energy will be given out in passing at oo C from density d, to density dz when , u ’ ~ is ~ Zless than EK (see Equation 16) and dz represents the density of the gas under standard conditions o€ pressure and temperature. The internal energy and the energy necessary to do external work must be allowed for and the equation for the calculation takes the form: 17. Total energy at o o C and 760 mrn pressure for a
Molecular Attraction. X V
641
+ + +
gram molecular weight of a stable gas = EE EK EI E,. Here EE is obtained from Equation 2 , EKfrom Equation I , EI from Equation 9, and E, = m r ~ . ’ ~ l / where $, do is the density of the solid a t the absolute zero. The values for this total energy for hydrogen, oxygen, nitrogen, and chlorine are shown in Table 5 , and the observed values obtained from the data previously given are shown immediately beneath the calculated values. The data for nitrogen are much the most accurate and the agreement there obtained between the calculated and the observed values is very pleasing. For hydrogen and oxygen the agreement is as good as could be expected and for chlorine the data used are very unsatisfactory. TABLE 5 Total energy at o o C
Y
do
31/z
EE EK E1 E, EE
+ EK + EI + E,
Observed
Hydrogen
Oxygen
1.407 0.08333 0.4368 542 .o 813.3 518.7 254.6 2129 I849
1.400 1.5154 1.1486
1
Nitrogen Chlorine
1.4064 1.0984 1.0318 541.1 541.6 813.3 813.3 542.1 520.7 1894.5 1606.6 3791 3482
I
,328
2 . I47 I . 2901
540.8 813.3 837.7 5684.4 7876 9239
The total energy in a complicated polyatomic substance could presumably also be calculated according to Equation 17 if there were no change of chemical energy, E,, to be considered. In considering the value of the ideas advanced in Part I11 of this paper it should be noted that the data are most accurate for mercury and nitrogen and that those substances give a very satisfactory agreement with the theory. Summary I . Some atomic specific heat curves are shown and discussed.
642
J . E. ilills
2 . The total energy added to a monatomic element from o o absolute to its melting point, including the heat of fusion, divided by the absolute temperature of the melting point, is nearly the same as the specific heat of the liquid element a t its melting point. 3 . Therefore the heat of fusion is supplementary to the specific heat of the solid, and the specific heat of a liquid monatomic element can be extrapolated to the absolute zero without great error so far as the total energy content of the liquid is concerned. 4. Atoms of monatomic elements in the liquid condition a t their melting point T contain an amount of energy approxi.itzateZy proportional to the temperature (usually between 7 . 5 T and 8 . 5 T calories per gram atomic weight). j . Those theories based upon the supposition that metallic electrons require notable specific heat energy are wrong. 6. The total energy added to a substance can be accounted for as being used in the following ways: to perform external work, to increase translational motion, to overcome molecular attractive forces, to increase motion within the molecule, and to overcome chemical forces of attraction. It is shown how the energy required for these different purposes (except the last) may be calculated. As proof of the correctness of the ideas advanced the total energy in a gram atomic weight of copper, zinc, mercury, aluminum, tin and lead, in the molten condition a t their melting points, is calculated. Also the total heat in mercury vapor a t its boiling point. Also the specific heat of liquid mercury. Also the total heat in a gram molecular weight of hydrogen, oxygen, nitrogen, and chlorine gas under standard conditions. The calculated values are compared with the observed. The agreement is satisfactory except for copper, zinc and chlorine where the divergences may be due to the data used. 7. If the divergences mentioned above are explainable as due to incorrect data, then the inverse square law of attraction holds true for molecular forces to the absolute zero for both liquid and solid.
Molecular Attraction. X V
643
8. The relation given in Equation 16 is derived. 9. The reciprocals of the distances apart of the molecules of liquid mercury between the temperatures -20" and 360" C
decrease almost exactly linearly with the temperature. IO. The heats of fusion of lead, phosphorus, hydrogen, gallium and lithium should be redetermined. Also certain data for copper, zinc, chlorine, and oxygen. Also it might be pointed out that a thorough experimental investigation of the energy changes of the liquids which Dr. Sidney Young has studied so carefully would prove of far greater benefit than ten times as much work spent in making heat measurements on miscellaneous liquids. University of South Carolina Columbia, S . C. May 15, 1917
