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T H E J O U R N A L OF I h T D U S T R I A L A N D ENGINEERIA’G C H E M I S T R Y
gases collected during explosions i n mines, a m a x i m u m of 30 minutes was required. All determinations were made b y simply passing t h e gas mixture back a n d forth i n t o a n Orsat pipette containing t h e solution a n d provided with glass tubes. T h e removal of t h e hydrogen probably should b e performed faster if t h e l a t t e r were shaken with t h e reagent as in a Hempel pipette. T h e colloidal palladium was obtained b y t h e Bureau .from Kalle & C o m p a n y , G e r m a n y : 6 g. cost $I j.84. I n t h e authors’ opinion t h e advantage of t h e method o v e r t h e use of palladium asbestos or palladium sponge i s in t h e fact t h a t i t never fails i n t h e a u t h o r s ’ experience t o work satisfactorily-something that, in the .authors’ experience, cannot be said regarding t h e use of t h e former substances.’ I n addition, i t can be placed in a n ordinary pipette of a gas-analysis app a r a t u s a n d does n o t have t o be heated in order t o excite i t t o action. I t s disadvantage lies i n i t s slowness of action a n d t h e somewhat troublesome method of regeneration of t h e used material. Hempel2 s t a t e s t h a t t h e solution slowly loses i t s absorbing power even i n t h e dark. H e recommends t h a t for each analysis small quantities of t h e freshly prepared liquid be used over mercury. T h e authors, however, have in satisfactofy use a t t h e present t i m e one solution t h a t was prepared i n J a n u a r y of t h i s year. T h e pipette has been surrounded with black paper. CHEMIC.4L LABORATORY, BUREAUOF M I N E S , PITTSBURGH, PA.
IODINE NUMBER OF LINSEED AND PETROLEUM OILS By W. H. SMITH A N D J. B. TUTTLE Received July 6, 1914
T h e linseed oil used in t h e manufacture of printing i n k is of t h e so-called “ b u r n t ” t y p e . There are t w o general processes for i t s manufacture-one i n which t h e oil is heated until t h e vapors t a k e fire a n d continue t o b u r n , t h e oil being allowed t o b u r n until i t a t t a i n s t h e desired viscosity; a n d a second i n which t h e oil is heated without permitting it t o t a k e fire. B u r n t oil is prepared i n several grades, all differing f r o m t h e raw oil i n a n increase of viscosity, specific g r a v i t y , a n d acid number, a n d a decrease i n t h e iodine n u m b e r . T h e longer t h e oil is heated t h e greater these differences become. I n t h e determination of t h e iodine value of some b u r n t linseed oils difficulty was experienced i n obtaini n g concordant results. Leeds4 has published some figures for iodine absorption of lithographic oils. K i t t 5 h a s also published a series of results which show decrease i n iodine absorption with increasing viscosity, b u t t h e figures do not agree with those given b y Leeds; their determinations were made according t o t h e Hub1 method.6 I n recent years t h i s method has been so generally replaced b y t h e rapid a n d more convenient 1 G . B. Taylor states, however, t h a t the colloidal palladurn solution does not work satisfactorily on gases obtained by distilling coal a t low temOct., 1914, p. 845. peratures. See THISJOURNAL, 2 Hempel, Walther, “Contribution t o the Determination of Hydrogen a n d Methane in Gas Mixtures,” 2. angew. Chem., 26 (1912), 1841. 3 Published b y permission of the Director of the Bureau of Standards. 4 J . SOC.Chem. I n d . , 13 (1894). 203. 6 Chem. Rev. Felt. u. Harz I n d . , 8 (1901). 40; J . SOC.Chem. Ind.. 10
