V O L U M E 28, N O . 11, N O V E M B E R 1 9 5 6
1793
Addendum
s
serious errom in past descriptions have come to our attention. The most serious of these completely negates the description of 1,2,5-trinitrophthalenu I (No. 82 in the series, published in June 1954) as a result of work by E . R. Ward and his ammiate, J. G. Hawkins, Leicester College of Technology and Commerce, Leicester, England. They have shown by means of infrared absorption t h a t the crystals for which the data were reported are actudly a, solid solution of 1,3,5-and 1,4,5trinitronaphthalene. The fact t h a t these two compounds form solid solutions and t h a t crystals of these two iscmers in a 1 t o 1 solid solution closely resemhle the cryst.als of the reported 1,2,5trinitronaphthalene has also been confirmed by microscopic fusion methods. The description published is, therefore, not t h a t of 1,2,5-trinitronaphthdenehut cf a solid solution of the 1,3,5-and 1,4,5- isomers containing a slight excess of the 1,4,5isomer. Ward also reports t h a t a small amount of the 1,5dinitranaphthalene may be present.. The second error involves the single crystal x-ray data for 4aminosalieylie acid published as description 98 in September 1955. Notice of this error came from Harry A. Rose, Lilly Research Laboratories, Eli Lilly and Co., and from Giordano Gi.mornello and his associates, F. Bertinotti and A. M. Liquari, Instituto di Chimioa Farmsceutica and the Centra di Strutturistica Chimica, University of Rome, Rome, Italy. T h e situation is best described by quoting from a letter received fram Giacomello. EVERAL
Figure 5. Typical crystals of lead azide I1 prepared in erysialliaing dish shown in Figure 4.
..-
F
We are surprised to see t h a t the unit cell dimensions given by
Krc and McCrone, apart from a different (and legitimate) choice of crystallographic axes, show rather large deviations from those reported by us in a paper on the structure of the mme compound published in Acta Cwstellographica [Bertinotti, F., Giacomella, G., Liquori, A. M., Acta Cwst. 7,808 (1954)]. I n fact, with the following index transformation:
H=2h-1
L =h the unit cell dimensions reported in our paper: Figure 6 . Orthographic projeotion of typical crystal of lead azide I1
OPTICALPROPERTIES Refractive Indices (5893 A,, 25' C.). e = 1.98 & 0.03. (3 = 2.14 i 0.01. y = 2.7 (cdcolattted from a,(3, and 2 V ) . ODtic Axial Andes (5893 A,: 25' C.). 2V = 67 =t3" (estimatkd fram curv&re of the &"shes). Dispersion. Inclined dispersion; one isogyte shows v > r and the other isogyre shows r > v . Optic Axial Plane. 010. Sign of Double Refraction. Positive. Acute Bisectria. y. Extinction, y A c = 32' in acute 8. Molecular Refraction ( E ) (5893A,; 25" C.). R (ohsd.) = 34.7.
a = 7.28A. b = 3.82.4. e = 25.33 A.
0
=
(1)
103"
become: a = 26.22A.
b c 6
= = =
3.82.4. 7.28A. 109.75"
(2)
which are not in agreement with those given in description 98:
q&
=
2.26.
ACKNOWLEDGMENT
The x-ray powder data on both forms were obtained by Irene Corvin. This program was supported by Contract No. DAI-l1-022-0RD-(P)-18 from the Officeof the Chief of Ordnance, U. S. Army.
a = 24.62A. b = 3.795 A.
c =
(3)
7.239 A.
8 = 108.6" Spacings calculated from dimensions 2 compare very well with those experimentally determined hy Xrc and McCrone fram the x-ray powder photograph, which we h v e reproduced with the compound crystallized aocording to the procedure suggested by these authors. It should, however, also he mentioned t h a t the powder data. obtained with a high resolution x-ray spectrometer show sdittinp of mme of the lines which are unresolved in the
LITERATURE CITED
(1) Aaaioff, L.V., 2. Kiist., in press. (2) Miles, F. D., J . Chern. Soc. 1931, 11, 2532. C a n ~ n r o u ~ r oof~ sorystallagraphie data for this Bection should be sent to Welter C. MoCrone, 500 East 33rd. St., Chicago 16, Ill.
graihic data which is 6eing made by ANALYTICAL CH
