July. 191 j
T H E J O C R S . I I , O F I.VDUSTRIAL A S D EAVGIXEERIiYG C H E M I S T R Y
S i c is correct for t h i s modification or variety. On t h e other h a n d t h e silicon a n d carbon i n t h e slategreen variety of silundum a d d u p t o only 91.07 per cent. This variety evidently does not correspond t o t h e formula S i c . TABLEVII-SCMMARY OF ANALYSES Carborundurn
poUND S i . . . . . . . . . . .
c . .. . . . . . . . .
29:39
TOTAL. . . . . . . . . . . . . . . . . . PI~K CXST THEORETICAL c,
,,. ,
,
,. J OTAL., . . . . . . . . . . . . . . . .
29,i8 " '
Steel-gray silundurn 69.53 29.89
__
99.42 Silicon carbide 70.22 29.78
__
100.00
Slate-green silundum 63.22 27.85
-
91.07 SirCiO 63.88 27.09
90.97
I t m a y h e assumed from t h e careful method of preparation, in which only pure silica. sugar-carbon, a n d graphite were used, t h a t t h e compound can contain only silicon, carbon, a n d oxygen. Since a temperat u r e of approximately 1600' C. must be attained for t h e reaction t o begin, practically all t h e air is expelled from t h e covered crucible; a n d further, since carbon monoxide gas is formed b y t h e reaction a n d sweeps o u t t h e last traces of air, t h e reaction product can consist only of carbon, silicon, a n d oxygen, a n d their compounds. T h e remaining 8.93 per cent m a y legitimately he assumed t o be oxygen. T h e percentage of oxygen corresponding t o t h e formula S i 4 C 4 0 is 9.03 per c e n t ; oxygen b y difference is 8.93 per cent, which is good agreement. .Attempts were made t o determine t h e oxygen cont e n t of t h e slate-green variety directly. T h e sample was placed with a pure metal, such as lead, steel, or copper in a vitrified clay boat in a combustion tube of a platinum-wound electric furnace, in which a temperature of 1300' C . can be easily attained. T h e air i n t h e a p p a r a t u s was displaced b y extremely carefully purified nitrogen, prepared from a m m o n i u m nitrite. T h e idea i n view was t h a t t h e molten metal would dissolve t h e substance a n d carbon monoxide or carbon dioxide might be liberated. Arrangement was macle for t h e monoxide t o be oxidized t o dioxide by passing through a hot t u b e containing cupric oxide. Owing t o t h e fact t h a t t h e sample i n each case floated on t h e surface of t h e molten metal, no reaction occurred, as evidenced b y t h e fact t h a t t h e K O H absorption a p p a r a t u s did not gain i n weight. .Is regards t h e relationship of silundum t o carborundum. results obtained in this paper indicate t h a t t h e steel-gray variety is a form of carborundum. T h e following facts may be mentioned: I-Silundum has t h e same chemical composition as car b or u n d u in. -.---Their chemical properties are similar.
