NOTES viations from the theoretical LH values for d / 2 T 2 = 1.0 are in the right direction. There is clea,rly no experimental basis for a claim of non-Lorentzian line shape, since all measurements are quantitatively in accord with theory for a Lorentzian lane of half-height width 0.29 c./sec., slightly distorted and broadened by sweep rates just slightly too rapid. It is interesting that, this is so, since the natural line width is only about 0.12 c./sec. Further and more careful studies of line shape on various n.m.r. spectrometers would perhaps enable a less tentative statement to be made. In this connection it may be noted that the Si29 satellites, for which J(SiZ9H) = 6.63 c./sec., may be used as internal calibration of sweep when the older-type i1.rrt.r. instrument is used; the shortterm instabilities in sweep rate would, however, make necessary a much larger number of measuremcnts than were required in the present work. I am grateful to Varian Associates, Inc., for making available this remarkably fine new ,spec'trometer, and to Mr. Robert Jones of that company for instruction in its use. T H E HEAT CONTENT AND HEAT CAPACITY OF BORON NITRIDE FROM 998 TO 1689OK.l IIY It. A.
MC.L)ONALD A N D
Tlifrmal Lnhornlory, The
11. R. STIJLL
Daw Chemical Company. .Widland,
Yol. 65 TABLE I ENTHALPY OF a-A1203" T.
Ilc
-
Obs.
OK.
Hzoms, cal. mole 1 NBS eq.6
+
VC I)?\ froni N B b
278.8 -353.8 -355.8 2.0 +0 329.6 615.8 619.9 - 4.1 -0 3346.4 448.3 3297.4 - 51.0 -1 5591 5 - 22 4 539.4 5569 1 -0 655.7 8803 2 8712 5 90 7 +1 761.3 11736 11671 6-5 +0 893.8 15455 15506 - 50 -0 1128.2 22436 22500 - 64 -0 $0 26758 (26726)' 32 1267.0 $0 1463.0 32902 (32765)' +137 1619.6 37849 (37630)' 4 219 $0 Molecular weight, 101.Mg. ni01e--~. * Funikawa, d rvf. 5. c Extrapolated.
+ +
+
56 66
55 40 04 56 3% 28 12 42 58 al.,
TABLE I1 OBSERVED ENTHALPY OF 13"' 111. -
7', "K.
IIT I l ? W ~ , rill. I l l O l t . I
HIYIL.I5,
T ,OK.
cal. mole- 1
279.5 279.5 408.3 455.6 656.3 884 3 902.9 Molcnd:tr
-83.2 -83.4 648.1 910 3 2545.1 4728.6 4893.0 weight, 24.83 g.
1120.7 1299.1 1381 . 8 1504 5 1603.0 1682.5 rnole
7183.3 9193.3 10160 11572 12802 13651
-I.
TABLE I11 HEATCAPACITY
Iliichiyair
Receiced M a y 4 , 1901
This work was undertaken tJo fill in the gap between the low temperature data of Ilworkin, Sasmor and Van ktsdalen2 and the high temperature investigation of Magnus and Danz3 arid to extend tho measurements to higher temperatures. Experimental
Deviation obsd. - calcd.
SMOOTHEL) ~ N T H A L l ' YA N D
O h
C" I
1'.
"li.
300 350 400 450 500 550 600 650 700 750 800 850 900 950
Hr Ldl
Ir Ill
