V O L U M E 21, NO. 8, A U G U S T 1 9 4 9
1017
C
C
&
Form and Habit. From fusion elongated rods parallel to direction of gron-th (assumed c). Interfacial Angles (Polar). 64", 123". (determined by W,C. McCrone). OPTICALPROPERTIES Refractive Indeses (5893 A.; 25'C.). a = 1.562. p = 1.707. y = 1.78 (calcd.). (Note. a and p as listed are the Cargille liquids which when saturated with o-aminobenzoic acid cause the crystals to disappear in those positions.) Optic Asial ringles ( 2 5 " C.). 2V = 68" (blue); 73" (yellotT); 75' (red). Dispersion. Very strong crossed disprision, r > v . Optic Asial Plane. 1 010. Sign of Double Refraction. ( - ). Acute Bisectrix. h. Estinction. p = 33 O from length. Fr510s DATA(determined by IT. C. lIcCrone). o-.kminobenzoic acid melts a t 145' C. with sublimation. The melt solidifies spontaneously on cooling. The crystals are alivays those of modification 111; they are characterized b\- large gas bubbles (Figure 1 ) and strong dispersion. The latter is manifest on those views showing an acute bisectriv interference figure; 2V = 68" (blue); 73" (yellow); 75" (red); ( - ) .
I
I
-a
B
LITERATURE CITED
(1) Groth, "Chemische Kiistallographie," T'ol. 4, p. 508, Leipaig C
Eneelmann. 1910.
I
(2) Kitaiiorodski, Iroest. A k a d . Vaitk. T..S.S.R. Atdel. Khim. S a i i k . . 1948, 278-89.
CORRECTION.I n the papcr entitled "hficroecope Hot Stage" by F. IT. Matthews [.\?;XI.. C"E\f., 20, 1112 11948)lTableI, page 11 15, "anthraquinone" should read "anthracene." F. \.T'. ?rf.4TTHERS
Evaluation of Catalysts for Catalytic Cracking
u-Aminobenzoic Acid
Figure 2.
Orthographic projections for modifications I ( u p p e r ) and 11 ( l o w e r )
c.
x - R . 4 ~ DIFFRACTIOX DATA(determined by IT. llccrone, J. Whitney, and I. Corvin)., Cell Dimensions. a = 11.66 A.; h = 16.04 A.; c = 7.18. Formula Weights per Cell. 8. Formula Weight. 137.13. Density. 1.367 ( 1 ) . Principal Lines d 8.21 6.42 6.16 5.38 4 74 4 37 4 11 3 96 3 76 3 66 3 56
I1Il
d
I111
0.11 0.24 0.30 0.25 0.52 0.06 Very weak Very weak 0.18 1 00 Very weak
3.38
0.12 0.36 Very weak 0.53 0.18 Very v e a k 0.11 Very weak Very weak Very v e a k 0.11
3.21 3.01 2.92 2.64 2.53 2.48 2.44 2.40 2.32 2.27
OPTICALPROPERTIES (deterFined by W.C. McCrone). Refractive Indexes (5893 A.; 25" C.). a = 1.560. p = 1.73. y = 1.76. Optic Axial Angles (25" C , ) . 2 8 = 46" (D). 2E = 84 (D); 81" (blue).; 85" (red); 7S1/zo(yellow); 73" (blue) ( 2 ) . Dispersion. r > v. Optic Axial Plane. 001. Sign of Double Refraction. ( ). Acute Bisectrix. b. hlolecular Refraction ( R )(5893 i.; 25' C.). = 1.68. R (calcd.) = 36.8. R (obsd.) = 37.9.
-
o-AMINOBENZOIC ACID 111
CRYSTALMORPHOLOGY (determined by IT. C. McCrone). Crystal System. llonoclinic.
SIR: I n the article by Rescorla, Ottenweller, and Freeman iAs.4~. CHEM.,20, 196 (1948)l we note some data given for iiatural catalyft which may be in error. 1. I n Table I the natural catalyst density aerated is given as 49.1 pounds per cubic foot, and free settled density as 46.5. The values would be about right were they interchanged. 2. I n Table I1 the sodium oxide content of natural catalyst is given as 0.32%. We believe this value is erroneously high. I n the same table the iron content is given as a 0.32% FeyOl. This value is apparently erroneously low. It appears that a typographical error is involved, as the iron and sodium contents in the case of both synthetic and natural are given as equivalent. 3. In Table 111 the sodium oside content of natural catalyst appears erroneously high, and we do n o t agree that the cracking activity data given are typical of the average natural catalyst from fluid cracking units. In this case the data may be correct because of certain characteristics of the oil fwd Atoclc to the unit in question. 4. At the bottom of page 200, the volatile matter contcnt of new natural catalyst is given as 25% when subjected to heat treatment at 850" F. .4ctually it would be espected t o test bctween 17 aiid 20% on such heat treatment. R. B. SECOR Filtrol Corporation Los .ingeles, Calif. ,SIP, :
hclmon ledging our negligence in ansivering the comments
of L)i . Semi we discuss them in the order listed in his letter of .lpiil 29. 1918, t o >mu. ~
