T H E -1OiYRlYAL OF 1 , Y D U S T R I A L A-YD E.\-GISEERISG
818
with the pressure to the extent demanded by the law of mass action as applied to the reaction C 2Hz = CH,.
+
According to this the value of p-(CH4)should be conP-(H2I2 stant a t any given temperature. I n all experiments, a t pressures varying from I O t o zoo atms., a value which was constant within the limits of experimental error was always obtained for this ratio a t any particular temperature, and when the same modification of carbon was used. I n some experiments, where a n amount of methane in excess of this value was added to the gas beforehand, decomposition took place until the same final value was obtained. Consequently this represents the true equilibrium constant. The amount of methane which a t atmospheric pressure is in equilibrium with hydrogen and graphite is a t r 2 o o 0 equal t o 0 . 2 4 per cent., and a t 1 5 0 0 ~ 0.07 per cent. For amorphous carbon, the "metastable" equilibrium values are 0.36 per cent. a t 1 2 0 0 ~and 0 . 1 8 At a pressure of n atmospheres, per cent. a t 1500'. the ratio of methane is n times a s great as a t I atmosphere. The values found in this work for the equilibrium constants in the case of carbon and graphite enable an approximate calculation to be made of the heat of reaction in the transformation of amorphous carbon into graphite. According t o Berthelot,I a t ordinary temperatures, this has the value 2840 cals. per gram atom. This value a t first falls with increase of temperature and a t some temperature below 1000' becomes zero. Consequently amorphous carbon is the stable form a t this temperature, but not a t ordinary temperatures. When heated above this stable point, it again becomes unstable, and consequently passes more or less rapidly into graphite with evolution of heat. The heat evolved in this transformation a t different temperatures can be calculated by means of a formula deduced by van't Hoff. I n this Q(r) = RTln-,K(1) K(2) where Q ( t ) is the heat of reaction a t the absolute temperature T ; R, the gas constant in calories ( I , 98) ; K ( l ) the equilibrium constant in the methane formula with amorphous carbon ; and K(2) that with graphite. We have from the above results the following values for the heat of reaction a t different temperatures: ~
\
TABLEIV.-PARTLY GRAPHITIZED CARBON. Temperature
-----
Centigrade. 12000 1300' 1400' 15.500
K(2),
-4bsolute. 1473' 1573' 1673' 1823'
KL'. 0 004 0 003 0 0023 0 0019
Qir)=RTInK(')
Compt. rend., 108, 1144 (1889)
GLASS FORMULAS : A CRITICISM.2 B y ALEXANDER SILVERXIAN.
Of the many manufacturing industries in which secret processes are developed, there is perhaps hardly another which equals t h a t of glass manufacture, and there is little doubt in the minds of those familiar with its methods that the formulas in actual use may be counted by thousands or even tens of thousands. Each manufacturer has made some change in a formula, either to follow the dictates of his fancy, or on the basis of sound scientific principles. Most of these changes belong to the former class, hence the thousands of recipes. Occasionally there appears on the market a new book on glass manufacture. This may belong to one of three classes: First, Publications dwelling entirely on technical principles; Second, Those dwelling to some extent on technical and scientific principles and furnish ing formulas; and Third, Books containing formulas only. The writer proposes t o confine his attention t o classes two and three, as he has found quite a number of unreliable recommendations made in books and journals of these types. The criticism is in some cases based on fixed scientific principles, but in most cases is backed by experiments conducted on a large scale, i. e . , not in small crucibles in the laboratory but in regulation pots in the factory. As examples of batches which have failed to yield the results claimed for them by their donors the following are cited: Hohlbaum, "Zeitgemasse Herstellung, Bearbeitung und Verzierung des Feineren Hohlglases," 19IO. Page 127. Rosaglas Nr. i . Sand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 R g . Kohlensaurer B a r y t . . ..................... 16 " Soda987c.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 " G o l d . . ................................... 12 g.
1480 1950 2450
32 0
Q ( t ) = Q(o) + T[c(j)-c(B)I where ci is the mean specific heat of the factors (in
1912
MAKCHESTER,ENGLASD.
'
I t has been shown by Kirchhoff that the heat of a chemical reaction changes with the temperature in the following manner:
Nov.,
this case carbon), and c p t h a t of the products of the reaction (in this case graphite). Since Q increases with the temperature, it follows that the mean specific heat of carbon a t temperatures abobe I I O O O is higher than that of graphite, and the difference increases rapidly with the temperature. The values given by Kunz' for carbon and by Weber1 for graphite show the opposite relation a t all temperatures above z o o o C., and are consequently not applicable a t these high temperatures. It would indeed follow from the values of Kunz and of Weber that amorphous carbon would be stable a t all temperatures. I t was also found that no saturated hydrocarbon other than methane is produced or is stable a t any temperature or pressure employed in this work.
K(z)
0 00245 0 0016 0 0011 0 0007
CHE-IIISTRE'.
Absolutely no sign of color was obtained though directions were followed implicitly. The writer of this paper has, in fact, not been able to obtain agold ruby unless reducing agents were added, and then 1.
Ann. Phq'sik, [4] 14, 327 (1904j: Ber. d . diem. Ges., 5, 303 (1872).
Paper presented a t t h e Eighth International Congress of Applied Chemistry, S e w York, September, 1912. 2
Nov.. 1912
T H E JOL-R-YdL OF I S D C S T R I A L A-YD E.\-GI-YEERISG
only with great difficulty when a lime batch was employed. On page 1 2 7 , Rosaglas Nr. 8 is given the following formula from its analysis: Sand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 K g . Kohlensaurer R a r y t . . . . . . . . . .. Soda 9 8 % . , , . . . . . . . . . . . . . . . . . . . . . . . . . Gold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16
.
‘‘
43 ‘‘ 12 g.
A reducing agent should have been employed, and as the analysis did not show its nature, a n organic or volatile inorganic body, or a combination of the two should have been recommended. Rosaglas Kr. 9, same page, was prepared according t o the formula: Sand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 K g Pottasche.. . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 “ K a l k s p a t . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 “ Selenig Saures Pl-atron., . . . . . . . . . . . . . . . . . . . 120 g. Arsenic.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200 “
and yielded only the faintest tinge of pink. On page 146 the formula for Granatrot Nr. 1 0 7 yielded a glass so soft t h a t i t ran from the blowpipe like water. It yielded not a vestige of color though this formula was employed as given: Sand. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 K g Soda . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 “ Zinkoxyd.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 “ Selen. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ’ / z ‘‘ .................. 1 “
All glasses thus far given and those ruby glasses yet t o be mentioned were “warmed in” repeatedly when no color made itself manifest on the first gathering and blowing. Pots were clayed up as tightly as possible and all precautions necessary for the proper working of ruby glasses were observed. These batches serve as examples from the Ilohlbaum publication. The claim may be made that furnace conditions were not proper as evinced by the soft nature of Granatrot K’r. 1 0 7 . The writer wishes t o say that he also tried some of Professor Hohlbaum’s Alabaster batches and found t h a t they were sandy and would not melt completely though treated in the same furnace. If the furnace was too hot for one and too cold for the other, it shows the importance of giving not only batches but furnace conditions necessary for the successful preparation of the glass. This criticism and those yet t o follow concerning publications b y other authors are not t o be construed as a reflection on the works referred to, many of which are most admirable in other respects, but are intended t o point out their weakness in publishing a lot of formulas, many of which will not work out in practice according to the directions accompanying them. The argument may also be made t h a t many formulas are valuable trade secrets and dare not be published. That is no excuse for publishing poor ones, or even good ones with some important direction withheld, Schnurpfeil, in “Die Schmelzung der Hohl, Schliff, Press, Tafel und Flaschenglaser, ” gives the following formulas which when tried yielded colorless glasses :
,
Page 9 7 .
CHEMISTRY.
ROSAROT 80.
819 ROSAROT 8 1.
Sand . . . . . . . . . . . . . . . . . 1 0 0 K g . Soda . . . . . . . . . . . . . . . . . 35 Kalk.. . . . . . . . . . . . . . . 14 “ Selen.. . . . . . . . . . . . . . . 55 g.
S a n d . . . . . . . . . . . . . . 100 Kg. Pottasche.. . . . . . . . . . . 15 ‘ I S o d a . . . . . . . . . . . . . . . . 18 “ Kalk.. . . . . . . . . . . . . . 15 “ Selen. . . . . . . . . . . . . . . . 100 8 .
ROSE ODER R O S E N R O T .
ROSA. 83. Sand . . . . . . . . . . . . . . . 1 0 0 K g . Soda.. . . . . . . . . . . . . . 32 “ K a l k . . . . . . . . . . . . . . 15 ‘* Selensaures S a t r o n . , 30 g.
82.
Lead . . . . . . . . . . . . . . . . . 100 Kg. Pottasche. , , , . , , , , , . , , 15 ( ’ Soda . . . . . . . . . . . . . . . . . 15 “ Marmor . . . . . . . . . . . . . 12 “ Saltpeter. . . . . . . . . . . . . . ‘/A “ Selen.. , , , , , , , , , . , , , . 125 E.
In none of the preceding four batches is a reducing agent employed. though this is essential for the production of a red color by selenium and in 82 the author even recommends the use of the oxidizing agent “saltpeter.” I n Sprecltsaal, 1 9 1 1 ,page 706. in the second answer to question 183, a batch is recommended in which litharge is used for a selenium-red glass, in presence of a reducing agent. With lead and a reducing agent present selenium has a tendency to blacken glass just as does sulphur or its compounds. The writer has noticed some five or six batches recommended in various publications, in which lead compounds are used with selenium, but objects to all of these because of the danger of formation of lead selenide. I n t h e third answer to question 183, same publication, a gold ruby batch is recommended without a reducing agent and in the fourth answer a lime-selenium batch is given. A4ccording to trials made, neither of these will work. The writer’s statements regarding selenium glasses are largely corroborated by Dipl. Ing. Fritz Kraze in his article entitled “Selenglas” which appeared during the current year in numbers 14 and 1 5 of Sprechsaal. Examples thus far given are confined to red or ruby glasses of the gold and selenium types. On numerous occasions copper-ruby batches have been published in which no reducing agent was prescribed. Many of the copper-ruby batches contain reducing agents in insufficient quantity, thus yielding green glass in which no amount of reheating will produce a red color. Ruby formulas have been made a n example of, because the most glaring and most numerous mistakes occur in t h a t class. Next in order are the opal and alabaster glasses, and no class escapes entirely, not even the colorless transparent glasses. To continue to cite incorrect formulas would only make this article monotonous. Even Henrivaux in his admirable volume has given formulas which do not yield the practical results claimed for them, and if all batches given in every other glass publication now in the market were tried not many would be found invulnerable. Several books containing only batches have been published anonymously, and one or two by men who claim to be expert glass-makers. Few of these batch books contain much that isworthtrying. Some formulas are wrong in principle, others in the proportion which the raw materials bear t o each other. If subjected to a close scrutiny hardly a single publication containing fromulas would go unscathed. The writer’s object in disclosures here made is t o bring
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 .
820
glass manufacture and glass literature to the high plane occupied by other exact sciences. If the worthy gentlemen whose publications have been criticized and others, whom the limits of this article have not included, will cooperate by publishing only formulas which are known t o be reliable, and will give proper directions for their use. they will materially assist in raising the plane of this important branch of science. UNIVERSITY OF PITTSBURGH, PITTSBURGH.
ON THE DENSITY OF SOME BORATE AND SILICATE GLASSES. By
EDWINWARDTILLOTSON,JR.
Nov., 1912
by fusing boric acid with the corresponding carbonates, it was difficult to drive off the last traces of carbon dioxide. This phenomenon was not observed in the preparation of the barium borates in this laboratory, although i t was difficult t o obtain borates containing high percentages of B,O,, free from minute bubbles, on account of the high viscosity of the melt. This doubtless explains some of the lower values for the observed density. The density of sodium oxides in silicate glasses is apparently somewhat greater than that assigned t o i t by Winkelmann. I n the following glasses the density was calculated, using 2.8 for sodium oxide:
Received July 1, 1912.
I n a former paper1 from this laboratory, attention was called to a method for calculating the approximate density of silicate glasses, and new density factors were proposed for several of the glass-forming oxides. I n calculating the density of some borate glasses prepared in this laboratory, it became evident that the density of boric trioxide in the glass is somewhat greater than the figure (1.9) given b y Winkelmann and Schott.2 Comparison with other published data, giving weight to the more careful measurements of density, showed 2 . 2 4 as the most probable value for the density of boron trioxide in these glasses. Table I shows the composition, the observed and calculated densities of several borate glasses from various sources. Table I1 shows the values for the density TABLEI. Density.
Percentages. Observed.
%Os. Ca(B02)~ Mg(B02)Z Zn(B0z)p Sr(BOd2 W 11
55.5 63.6 46.2 40.3 41.0
W 16
42.8
B a O 2 B ~ 0 8 46.37 Ba04B208 6 3 . 4 0 Na&i,Or 69.3
{
CaO 4 4 . 5 MgO 3 6 . 4 ZnO 5 3 . 8 SrO 59.7 ZnO 5 9 . 0 Ala, 5 . 2 PbO 5 2 . 0 PbO 53.63 PbO 36.60 NalO 3 0 . 7
2.7711 2.5201 3.320’ 3.254’ 3.5272
Calculated.‘ 2 .SO 2.40 2.99
....
3.17
Calculated.6 2.807 2.667 3.358 3.258 3.532
3.6912
3.42
3.785
3.5223 2.9223 2.3704
3.12 2.595 2.01
3.526 2.982 2.387
Tamman-Krysfallisieren und Schmelzen, p. 50. Winkelmann and Schott, loc. cit. a Tillotson. 4 Day and Allen, “Isomorphism and Thermal Properties of t h e Feldspars.” 5 Using Winkelmann’s factors. 6 Using modified factors. TABLE 11. Winkelmann Modified factors. factors. SO2. .2.3 2.3 Ba08. 1.9 2.24 NazO.. 2.6 2.8 CaO ............. 3 . 3 4.1 MgO 3.8 4.0 AlzO3.. 4.1 2.75 1 2
............
............
.......... ............. ..........
employed by Winkelmann and Schott and those now proposed for giving a more accurate calculated value of the density of the glass. Inspection of the figures in Table I shows that in the case of the carefully prepared borates the observed and calculated densities are in good agreement. Tamman3 observed t h a t in the preparation of these borates THIS JOURNAL, 3, 897 (1911). 2 Ann. d. Phys. und. Chem., 49,401 (1893); 61, 697 (1894); “JenaGlass a n d I t s Industrial Application,” Hovestadt (English Edition), p. 148. 8 Krystallisierelt und Schmelzen. 1
-
Percentages. No. W 25 W 8
SiO2. 71.0 68.3
ZnO ZnO
12 Na2O 1 7 . 0 5 . 0 NazO 1 0 . 8 A1203 1 . 0 PbO 8.1
Obs. 2.572 2.629
Density. Calc. 2.566 2.639
This is further illustrated b y the soda barium silicates shown in Table 111. TABLE 111. SiOz. Per cent. 74.50 66.15 61.70 53 .OO 71.70 67.60 64.55 61.30 58.30 55.34 52.46 49.95 46.91 44.25 79 .oo 75.85 67.45 62.60 57.20 51.14 36.84 1 Using 2 Using
BaO. Per cent.
...
NazO. Per cent. 25 .SO 20.85 18.50 13.40 22.65 19.85 17 .OO 19.50 12 .oo 9.56 6.94 4.55 2.29
Density. Found.
2.437 13.00 2.64 19.10 2.752 33.60 3.06 5.65 2.491 2.633 12.55 2.759 18.45 2.824 24.20 2.934 29.70 3.072 35.10 3.212 40.60 3.367 46.00 3.476 50.80 ... 3 . 6 5 55.75 15.85 5.15 2.46 14.80 9.35 2.514 12.20 20.35 2.722 10.80 2.845 26.60 9.20 3 06 33 60 41.50 7.36 3.224 3.95 60.40 2.76 Winkelmann’s factors. modified factors.
Calc.’
Calc.2
2.37 2.59 2.725 3.03 2.45 2.57 2.69 2.80 2.925 3.05 3.195 3.35 3.50 3.67 2.43 2.50 2.72 2.84 3.01 3.265 3.88
2.41 2.625 2.755 3.055 2.50 2.615 2.72 2.83 2.96 3.08 3.22 3.37 3.51 3.69 2.455 2.523 2.73 2.87 3 04 3.245 3.90
Error.1 Error.2 Per Per cent. cent. f2.O +10 +2.0 +0.6 +2.0 -0.2 +1.0 +0.1 +1.4 -0.2 + 2-~ .4 c 0.. .7 +2.5 +1.4 +0.8 -0.2 +0.3 -0.9 f0.7 -0.2 -0.2 +0.5 -0.1 +0.5 -1.1 -0.8 -0.5 -0.5 +0.2 +1.2 -4.4 +0.6 -0.3 +0.1 +0.2 -0.9 +1.6 +0.7 -1.3 -0.9 +1.8 +1.2
It will be seen that the observed and calculated values for the density of these silicates are in very good agreement and as the compositions of the glasses vary over wide limits, it is evident that the method is capable of giving excellent results with a large variety of glasses. SUMMARY
I. The densities of some pure borate glasses have been examined and a n empirical factor determined for the density of B20, in the glass. The factor adopted is 2 . 2 4 instead of 1.9as given by Winkelmann. 2 . The densities of some soda barium glasses have been studied and the factor 2.8 for the density of Na,O has been adopted in place of 2.6 employed b y Winkelmann. DEPARTMENT O F INDUSTRIAL RESEARCH, UNIVERSITYOR KANSAS, LAWRENCE.
I
