Sept., 1 9 1 2
T H E J O U R S A L OF IAVDC:STRI.4L 44AYDE.l'GISEERI.VG
skinned over to a considerable extent and gained 2.30 per cent. The blank showed only light skinning and an increase of but 0 . 2 7 per cent. TVhaLc oil gained 0.6 per cent. in 6 hours. The appearance and odor were not changed Coriz oil.-Eight hours heating was necessary in order to obtain a constant weight; a very small loss (0.04 per cent.) resulted, due possibly to the presence of water in the sample. There was no apparent change in either odor or appearance. S o y a oil.-After 7 hours the sample to which carbon tetrachloride had been added showed an increase of 0.j per cent., while there was no gain in the blank. After heating for 3 1 / ~hours longer, the mixed sample had gained I per cent. and the blank 0.;3 per cent. I t therefore appears that Soya oil will stand heating for some time before giving any indications of oxidation. Heating somewhat intensified the odor. DEPARTMENT O F CHEXISTRY. COLLEGEO F THE CITY OF NEW Y O R X . .
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n y EDWIN W A R D TILLOTSON, JR. Received July 1 , 1912.
I n a former paper1 from this laboratory, a simple and convenient method was described for measuring the surface tension of molten glasses. This method consisted, briefly, in the determination of the relation between the weight of the drops falling from glass fibers of known diameter, which were lowered vertically into the carefully regulated flame of a blast lamp. I t was found that the weight of the drop was within limits a parabolic function of the diameter o f the fiber and t o be expressed by the following equation: W = aD $D2 when W is the weight of the drop, D the diameter of the fiber, a a factor proportional to the surface tension and, b9 a factor dependent on the cohesion of the molten glass. This factor ;? seemed to be nearly constant for a considerable number of borate glasses, although it varied widely for some of the silicates. The present paper is a record of surfac,e tension determinations made on some sodium silicates, soda lime and soda-barium glasses, and also soda barium glasses containing boric oxide. For these measurements about ten fibers were drawn from each glass. varying roughly from 0.10--1.00 mm. in diameter, the drops formed in the manner previously described, and weighed. I n every glass examined the parabolic relation of the diameter of fiber to weight of drop was observed and it was found that this was satisfied by a value of ~j for ?; in all of the glasses. This value for is not an exact one. nor can i t be accurately calculated from so few measurements. There are many causes which contribute to variations in the weight of individual drops. Inhomogeneity of the glass, errors in measurement of the diameter of the fiber, momentarychanges in the condition of the flame-all may effect the weight of the drop. It is therefore necessary to make many measurements on the same glass in order to fix the exact value of p. But since for these glasses 1
Tillotson, THJSJOURNAL, 8, 631 (1911).
65 1
a difference of one unit in ,9 produces a variation in the surface tension of only 2 dynes and since this is small in comparison to that introduced by variations of individual drops, the value 1 5 was adopted for p in all of these glasses That this procedure was justified is shown by the fact that the values for a were neither progressively higher nor lower as the diameter of the fibers increased. TABLEI -SODIUM SILICATEGLASSES.
T = dynes per cm. SiO?. Per cent
I\-a*O. Per cent.
Obs.
50 7 40 8 33 6 26 9 25 5 22 5 22 7
142 142 136 133 138 138 137
49.3 59.2 66.4 73.1 74.5 77.5 77.3
TABLE II.-sODA-RARIUII
Calc. 145 142 139 137 137 137 136
GLASSES. T = dynes per
Si02. Per cent.
BaO. Per cent.
Na20. I'er cent.
~1x1.
Ohs.
Calc.
144 145 150 164 153 155 138 143 151 150 148
140 144 148 151 155 159
~
ON THE SURFACE TENSION OF SILICATE AND BOROSILICATE GLASSES.
+
CHEMISTRY.
70.10 66.15 61.70 57.30 53 .OO 48.37 71.70 67.60 64.55 61.36 58.30
6.50 13 .OO 19.80 26.57 33.60 40.70 5.65 12.55 18.45 24.17 29.70
23.40 20,85 18.50 16 13 13.40 10.88 22.65 19.85 17.00 14.47 12.00
TABLE III.-sODA
73.60 72.32 70.85 69.30 67.40 65.20
CaO. Per cent.
Sa*O. Per cent.
2 .50 5.18 8.25 11.70 15.60 20.20
23.90 22.50 20.90 19.00 17.00 14.60
TABLE IV.
--
= dynes per cm.
QbS.
Calc.
137 152 146 158 166 172
141 146 15 1 158 165 173
*
T SOy. Per cent. 63.94 52.76 45.70 36.45 31 77 24.40
B203.
Per cent. 3.88 6.42 8.10 10.62 11.64 13.26
BaO. Per cent. 15.78 26.90 34 . 5 0 44.75 48.40 55.80
143 146 149 152
LIME GLASSES.
T SOs. Per cent.
140
= dynes per cm.
Na20.
Per cent. 16.40 13.92 11.70 9.18 8 37 6.54
Obs.
Calc.
145 142 145 153 159 155
142 146 148 153 154 157
The glasses studied consisted of seven sodium silicates, eleven soda-barium glasses and six soda-lime glasses When the results of these measurements were plotted in a system in which the composition of the glass was represented by the abscissas and the surface tension by the ordinates. i t was observed that the surface tension was roughly a linear function of the composition. I t was therefore possible to compute the surface tension which each oxide showed in its combination in the glass, and with these factors t o calculate the surface tension for the several glasses with the aid of the following formula:
T = alpl + a,p, + aapa,etc., in which T is the surface tension of the glass, a,, a2,a 3 , etc., are the surface tensions of the several oxides and p l . p,. p 3 , etc are the percentages of the respective oxides In the glass. The figures given in t h c tables
.
T H E J O C R N A L OF I N D U S T R I A L A-VD ESGIAYEERIL\;G C H E M I S T R Y .
652
under “calculated” are the values of the surface tension obtained in this way, using the following fa,ctors: Si02 B203
BaO ’
CaO Xa,O
129 45 195 323 160
Sept., i912
soda-barium silicate glasses and of some soda-barium borosilicate glasses has been measured. 2 . The surface tension of glasses is roughly a linear function of their composition. 3. The surface tension of silicate and borosilicate glass may be calculated with a fair degree of accuracy from the chemical composition, using the following values for the surface tension of the oxides: SiO,, 129; B,O,,4 j ; RaO, 195; CaO, 3 2 3 ; Na,O, 160.
I n Table I are shown the results of measurements on sodium silicates. The first two columns show the composition of the glass; column three shows the observed afid column four the calculated surface tension. DEPARTMENT O F IXDUSTRIAL RESEARCH, UNIVERSITY OF KANSAS, Table I1 shows the data obtained with the sodaLAWRENCE. barium glasses, and Table I11 that for the soda-lime glasses. I n both of these tables the first three columns THE DETECTION AND DETERMINATION OF CYANOGEN AND give the composition of the glasses and the last two HYDROGEN CYANIDE. columns give respectively the cbserved and calculated R y F. H . RHODES. value of the surface tension. 111 Table IV are shown Received June 6, 1912. some soda barium glasses containing boric oxide. The usual method for the detection and determinaThis series of glasses is especially interesting since it tion of cyanogen and hydrogen cyanide in the presence permitted a very wide range in the proportions of the of each other is based upon the difference in the prodseveral oxides and offered a severe test for the validity ucts of the reaction of cyanogen and of hydrogen of the additive nature of surface tension. cyanide with a solution of potassium hydroxide. I n the measurements. in the tables given above, i t When passed into a solution of potassium hydroxide, is found that the observed and calculated surface hydrogen cyanide is quantitatively converted into tensions differ, for the most part, by not more than potassium cyanide, whereas cyanogen forms equitwo or three per cent. This is not surprising since , molecular amounts of potassium cyanide and potassium thesurface tensionsof liquids are, as a rule, very sensitive cyanate. to the presence of small amounts of impurities. The The usual method for the detection of cyanogen in glasses doubtless contain aluminum silicates and the presence of hydrogen cyanide consists in absorbing other impurities taken up from the crucible, which the gases in a solution of potassium hydroxide and may perhaps affect the surface tension quite out of testing for potassium cyanate Potass urn cyanate proportion to the amount present. The experimental may be detected by acidifying the solution. heating error is not large when ten or more fibers are employed, to hydrolyze the cyanic acid liberated by this acidificaas shown by the following measurements which were tion, and testing for the ammonia formed by this repeated, unknown to the worker, after several other hydrolysis. glasses had been investigated. No. I is the second of The customary method for the determination of the alkali silicates, as given in Table I and No. z is cyanogen in the presence of hydrogen cyanide is based. the last one of the same table. upon the same reactions as the qualitative method ( CK), T. just described. The gases are absorbed in a solution 1. 45.4 141.6 of potassium hydrox’de. the potassium cyanate is 140.8 45.1 decomposed by the addition of an excess of a strong 2 . 43.7 136.3 43.8 136.6 acid, and the resulting ammonia is determined by the On comparing the values of the surface tensions of addition of an excess of alkali and distillation into the pure oxides, as calculated from that of the glasses, standard ‘acid. Both the qualitative and quantitative we find in general that the acid-forming oxides, SiO? methods just de‘scribed are tedious, and are liable t o and B,O,, show lower surface tensions than the basic error because of the possibility of the formation of oxides. Placed in descending order they are as follows: some ammonia by the simultaneous hydrolysis of CaO. 3 2 3 ; NaO, 1 9 s ; N a O , 1 6 0 ; SiO,. 1 2 9 ; B,O,, 4 5 . some of the hydrocyanic acid liberated upon the acidiIt is interesting to note that this surface tension of fication of the solution containing potassium cyanide. Wallis1 states that when hydrogen cyanide is passed B,O, is the same as that obtained by direct measureinto an acidified solution of silver nitrate i t reacts ment on the fused boric oxide, and a little over one-half of that given by Quincke‘ (84.5). Inasmuch as the quantitatively with the silver nitrate to precipitate surface tensions of the lead borates previously de- silver cyanide. He also states that cyanogen does scribed* do not show any regular relationship, this not react with an acidified solution of silver nitrate, coincidence in the two values of the surface tension and that any cyanogen which dissolves as such in the reagent may be removed practically completely by of boric oxide probably has Lttle significance. passing a current of air through the solution. Upon this I n conclusion, the writer desires to acknowledge his indebtedness to Mr. J . D. Malcolmson for his generous difference of behavior of cyanogen and of hydrogen cyanide toward silver nitrate, Wallis based a method assistance in these measurements. for the detection of cyanogen and of hydrogen cyanide SUMhIARY. I . The surface tension of a number of suda-limc, when these gases are present t-)gether in a gas mixture, but he carried the work n o lurthcl- than t o show -the ’ Quincke. Pow. Aniz., 158, 141 (1869). illutson. I.r.c
CII
Wallis, An%. Chem., 546, 353 (1906).
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