Junuar?, 1932
I N 1) ti S T 1%I h I, A N U
E N G I N 15 E it 1 U 0 C 11 E M 1 S T Il Y
(IS) Mhrvin, T.0.. o t al., "lluorspar," U. S. TsriFl Coin.. Rapt. to the President, 1928. , "1,oa Reserves Mondihles en I'hoaphates;' Vol. I , 13. I:% Bureau I41,h internat. Grot. Con~resa,Madrid. 1928. 40-K,1!15-3?': (1917). (18) i'ardee, J. T.,U. S. Geol. Si (19) I'ardee, d. T.,l b u l . . 7154, I (20) Roynolds. D. S., Jacoh. I lhsrlI.i~.\~rios
Ow or t l w iriost promising l i i i e i i,f attack is tho use of lrigli viicuuiii. Tsually, the lower the tciiiperature tlie grenter ilie volatility differences IrrLtwecii materials, arid, Ii(mce,, tlie casior tlie rcparat,ion by distillation: hit lalxiratory workers Imw iwt. t a h r adranttig(:r.uf this fact t,o the csteiit they h d d . Siirw tlie dwp iii triuperatiirc can l i e sccunxl (mly b y d r o p in pres-
sure, and since la ", pressure decrea are r i e e r s s a r y 1.0 p r o d u c e iiiarked c h a n g e s i i i teixiperiiturc, it is proba b l e t h a t vaI:uIIIII has riot heeii used itlore w i d e l y h e muse workers lia\.e t r i e d i r r r ~ d c r ti! a V~CUUIII aiid fwiiid little ad va ii t a g e . Ilowever, with tlre d e v e l opiii e n t o f ino d e r 11 11 i g t i v a e n ii ni t e r:hni c , it is possible to achieve r c s II I t s 11 i t h e r t, o u II dreanred. It will be necessary, it i s true, to use rretification under vaeuum, the fir31 lhwr, tho lab
