418
S I G X Y S D W:AT.DBOTT.
T h e furnace is an up and ctonii draught made by Geith. of Coburg, Germany, from designs of Seger, and has a zone of at least seventyfive cubic inches that is perfectly unifonii in lient. T h e dish of borax glass and the pyrometric trials were placed i i i the center of this zone. T h e dish lost in three hours 0 . I I I j grariis or I .47 per cent S C X M . 4 K l ' O F THE KESI'LTS ~>l%T.LISF:Il l?Y P K U I . Amoirnt of borax Duratiori Jlaxirriuni M e a n s of riieasuririg glass. of heat. temperature. the teniperntiire. qrarns. hours.
2.3056 5.7698 9.2036 7.5803
60 48 26
3
1410- C . 1350- C . 1ojo: C . 954 c .
Seger's coiie. So. 9. Seger's colic, SO.7 . Alloy 1 5 'x, Ax 85 t i u .
'x,
A#.
[COSTRIBUTIOP;S F*ROll THE CHE\IIC.&I, L.AROH.4TOKY OF T H E r S I V X K S I T Y
OF
C\ISCIXN.\TI.
SLV1.l
ON THE VOLATILITY OF SODIUM FLUORIDE.' BS s I G > t V S l l
T
\vALDIIWTT,
1'11.1).
HE analyses mentioned i n Experiments A I11 am1 -1I V of
the foregoing communication did not at first give perfectly satisfactory results. In the eiideavor to ascertain the cause of the deficiency, the analytical iiietliod eniploped was subjected t o a careful examination. This method, as described by A. Iieischle,2 is based on the principle that boric acid can be easily driven off from a borate by mixing it with six times its weight of resublimed aniiiioiiiuiii fluoride, and heating carefully until all the boron is volatilized as amnioniurii borofluoride. T h e residue, consisting of the. fluorides of the metals that were combined with boric acid, is then treated with sulphuric acid arid evaporated to dryness. T h e sulphates are ignited ant1 weighed, and the amount of boric acid, if desired, is calculated from the difference between the original weight and the weight of the oxides present in the sulphates. 1
Read before the Cinciiiriati Section. February 15. 1 8 ~ 4 . Keischle, Zf'lschr.a n o r g . Cheni., 4 , 111-116.AIM. i i r j . Chenr. So(..,1\93. (abstracts)
2 .4.
p. 4~91.
O N THE VOLATILITY OF SODIUM FLUORIDE.
419
T h i s process, according to comparative tests made by Reischle, has proved to be the best of all known methods for determining boric acid indirectly. Several analyses carried out in the laboratory of the University of Cincinnati confirm its reliability. Experience shows, however, that a few precautions must be closely observed in order to insure accurate results. T h e ammonium fluoride employed must be resubliined, or a t least the residue left on sublimation must be carefully determined and the necessary deduction made from the final weighing. Another source of possible error seemed to lie in the volatility of the alkaline fluorides a t a comparatively low temperature, and some abnormal results recorded by Reischle, were probably due to this cause. As nothing has been published on this subject it seemed desirable to examine closely the behavior of sodium fluoride, at least a t varying temperatures, and bring the results of the study to bear upon the details of the Reischle method. T h e sodium fiuoride employed was chemically pure and procured from C. Schuchardt in Gorlitz. T h e following experimental results were obtained :
I. NaF not dried, =0.5605 gram. Heated over the Bunsen burner, =0.5495 gram. Heated again for two minutes, =0.549 gram.
This weight, 0.5490 gram of dry N a F , was further heated as follou3 : Time of heating, minutes. 2
6 2 12
Loss each time,
Mode of heating.
................
gram. 0.0040
Moderate blast flame Bunsen burner with chimney, crucible slightly uncovered.. 0.0020 Blast-flame, crucible uncovered.. 0.0167 Bunseii burner with chimney, crucible slightly uncovered.. o.Oo60
..............
.... ..............
Total Total loss, lossin gram. p e r cent. 0.0040 0.71
o.Oo60
1.0g
0.0227
4.1
0.0287
5.2
11. NaF not dried, =0.2775 gram. Heated over Bunsen burner to constant weight, = 0.2714 gram.
This weight, 0.2714gram of dried N a F , was further heated a s follows :
E D G A R F. S M I T H A S D H E N R Y E . SPESCER
320 Time of heating. iiiiuutes.
6
I,>, e a c h 1ifI:e. ;?nlll
>Iode of heating.
Bunsen b u r n e r , crucible slightly
‘rotxl io.*.
