VOL. XXVI.
[JANUARY,
1904.1
No.
I.
THE JOURNAL OF THE
AMERICAN CHEMICAL SOCIETY. REPORT OF T H E INTERNATIONAL COMMITTEE ON ATOlllC WEIGHTS. Received November 8 , ,903
THEInternational Committee on Atomic IVeightsl has the honor to offer the following report : I n the table of atomic weights for 1904 only two changes from 1903 are recommended. The atomic weight of caesium has been slightly modified to accord with the recent determinations by Richards and Archibald, and that of cerium in confolrmity with the measurements by Brauner. The value for lanthanum is still in controversy, and any change here would therefore be premature. The same consideration may also be urged with regard to iodine. Ladenburg has shown that the accepted number for iodine is probably too low, but other investigations upon the subject are known to be in progress, and until they have been completed it would be unwise to propose any alteration. Many of the atomic weights given in the table are well known to be more or less uncertain. This is especially true with respect to the rarer elements, such 'as gallium, indium, columbium, tantalum, etc. But some of the commoner elements also stand in 1 The original members of the committee take great pleasure in announcing the addition to their number of Professor Henri Moissan. They are confident that this increase will meet with universal approval.
2
REPORT O F INTERNATIONAL C O M M I T T E E
need of revision, and we venture to call attention to a few of these. Among the metals, the atomic weights of mercury. tin, bismuth and antimony should be redetermined, for the reason that the existing data are not sufficiently concordant. Palladium also, on account of discrepancies between different observers, and possibly vanadium, for which the data are too few, deserve attention. Among the non-metals, phosphorus has been peculiarly neglected ; and our knowledge of the atomic weight of silicon rests upon a single ratio. In the lztter case, confirmatory data are much to be desired. Upon any of these elements new investigations would be most serviceable. There is m e other point to which we may properly call attention. Many of the ratios from which atomic weights have been calculated, were measured in vessels of glass, by processes involving the use of strong acids. In such cases the solubility of the glass becomes an important consideration, even when no transfer of material from one vessel to another has occurred. A slight conversion of silicate into chloride would cause an increase of weight during the operation, and so introduce an error into the determination. Such errors are doubtless very small, and still they ought not to he neglected. Now that vessels of pure silica, the so-called quartz-glass, are available for use, they might well replace ordinary glass in all processes for the determination of atomic weights. An investigation into the relative availability of the two kinds of glass is most desirable. F. W-.CLARKE, (Signed) T. E. THORPE, KARL SEUBKRT, HENRIMOISSAN,
Committee. INTERNATIONAL ATOMIC WEIGHTS. Aluminum ........ Antimony ........ Argon ............ Arsenic.. ......... Barium .......... Bismuth.. ........ Boron ............ Bromiue . . . . . . . . . Cadmium . . . . . . . . . Caesium . . . . . . . . . .
0 = 16.
l i -=I.
A1
27.1
Sb A As Ba Bi B Br Cd
120.2
26.9 119.3 39.6 73.4 136.4 206.9
Cs
39.9 75.0 137.4 208.5 11.
79.96 112.4 132.9
10.9
79.36 111.6
131.9
ON ATOMIC WEIGHTS
.......... ........... ..........
Calcium Carbon Cerium Chlorine Chromium Cobalt Columbium Copper Erbium ........... Fluorine Gadolinium Gallium .......... Germanium Glucinum Gold ............. Helium Hydrogen Indium ........... Iodine Iridium .......... Iron .............. Krypton ......... Lanthanum Lead Lithium Magnesium Manganese Mercury Molybdenum Neodymium Neon Nickel Nitrogen ......... Osmium .......... Oxygen .......... Palladium ........ Phosphorus ....... Platinum ......... Potassium ........ Praseodymium Radium Rhodium Rubidium Ruthenium ....... Samarium ........ Scandium Selenium
.......... ........ ............ ...... ........... .......... .......
.......
........ ........... ........ ............
Ca
C Ce c1 Cr co Cb cu
Er F Gd Ga Ge G1 AU
He H In I Ir Fe Kr La Pb
....... ............. .......... Li ...... Mg ....... Mn .......... Hg
..... ...... ............ ...........
.... .......... ......... ........
........ .........
Mo Nd Ne Ni N
os 0 Pd P Pt K Pr Ra Rh Rb Ru Sm
sc Se
.
3
.
0 = 16.
H =I
40 . I
39.8 11.91 139.2 35.18 51.7 58.56 93.3 63.I 164.8 18.9 I55 . 69.5 71.9 9.03 195.7 4.
12.00
140.25 35.45 52.1
59.0 94. 63.6 I 66 '9 . 156. 70 72.5 9 I '97.2 4. 1.008 114 . 126.85 193.0 55.9 81.8 138.9 206.9 7.03 24.36 55.0
.
.
200.0
96.0 143.6 20
.
58.7 14.04 191. 16.00 106.5 31.0 194.8 39.15 140.5 225
.
103.0 85.4 101.7 150 44.1 79.2
.
.
1 ooo
113.1 '25.90
191.5 55.5 81.2
137.9 205.35 6.98 24.18 54.6 198.5 95.3 142.5
19.9 58.3 13.93 189.6 15.88 105.7
30.77 193.3 38.86 139.4 223.3 102.2 84.8 100.9 148.9 43.8 78.6
4
.
W GEORGE W A R I N G .
Silicon . . . . . . . . . . Silver ............ Sodium ........... Strontium ........ Sulphur .......... Tantalunl . . . . . . . . . Tellurium ........ Terbium .......... Thallium ......... Thorium ......... Thulium ......... Tin .............. Titanium . . . . . . . . Tungsten . . . . . . . . Uranium ......... Vanadium . . . . . . . . Xenon ........... Ytterbium . . . . . . . . Yttrium . . . . . . . . . . Zinc . . . . . . . . . . . . . . Zirconium ........
Si Ag Na Sr S Ta Te Tb T1 Th Tnl Sn
Ti
.4
28
107.93 23.oj 87.6 32.06 183 . 127.6 160. 204.I
202.6
232.5
230.8 169.7 118.1 41.7 182.6 236.7
171. I 19.0
\I;
48 . I 184.
U
228 j
\’
28.2
107.12 22.88 86.94 3733 181.6 126.6 158.8
.
51.2
.
j0.8
Xe
I28
127.
Yb Yt Zn Zr
173.0
171.7 88.3 64.9 89.9
89.0 65.4 90.6
T H E VOLUnETRIC DETERfllNATlON OF ZINC
.
BY W . GEORGEWARING Received October ( 5 . 1903
THEdelicacy and precision of the ferrocyanide titration of zinc in properly conditioned solution is almost wholly negatived by inexact methods used for the separation of zinc from interfering elements and by misleading. contradictory and useless directions given in text-bmks. An inquiry into the causes of extraordinary discrepancies in zinc determinations made by a number of public analysts. zinc works chemists. and college instructors upon identical samples has led the writer to prepare this paper. in which he endeavors first to discuss the sources of error peculiar to zinc determinations by the ferrocyanide volumetric methods. adding in the sequel. a description of the methods followed in his laboratory at \Vebb City. Mo., for the determination of zinc in various combinations . SOURCES OF ERROR
Losses may result from : ( I ) Volatilization of zinc as chloride .
.
