T H E JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY
580
T h e specific gravities a n d solidifying points are t a k e n exactly as described previously. H . Interpretation of Results-After t h e tests show t h e point t o be within t h e determinative areas t h e method of interpolation is as follows: If t h e plotted point occurs in t h e lower set of curves a line is drawn through t h e point normal t o t h e curves between which it lies. T h e distance from curve t o curve is measured accurately along t h i s line a n d t h e fractional distance of t h e point is interpolated i n t o per cent phenol. If t h e point occurs in t h e upper set of curves, t h e line is drawn t h r o u g h t h e point parallel t o t h e nearest of t h e d o t t e d converging lines, t h e linear distance measured a n d t h e percentage interpolated as before. If mixtures are made, t h e calculations are somewhat complicated a n d t h e following formula may be used: Let A = per cent phenol f o u n d in mixture B = Grams " t o 197'" fraction taken C = Grams pure phenol taken X = per cent phenol in " t o 197"' fraction
x=
~
( B +~c)--_IPsc B
T h e per centphenolinthe"t0 19; '"fraction multiplied by t h e weight of t h e fraction gives t h e weight of total phenol i n t h e oil or crude acid t a k e n . A specimen test on acid with t h e recorded d a t a may be shown as follows: TAKEN:Crude Acid, 300 g. Distilled 170-190;. ...................... 60.65 g. 190-202 ....................... l i 8 . 0 5 g. 190-202° redistilled t o 197'. ........................ 78.05 g. Total under 1 9 i 0 . ,...................... 138.7 g. = 4 6 . 2 per cent 1.0$02 Sp. gr. a t 25/25' C.. Solidifying point.. ......................... 20.4 These constants are indeterminate. t o 197' fraction.. . . . . . . . . . . . . . 25 g. MIXTURE Pure phenol.. . . . . . . . . . . . . . . . 25 g. Sp. gr. a t 45/45' C . . 1.0576 31.7' C. Solidifying point., ......................... Phenol in fraction mixture (from curve). . . . . . . . . . . . . . 84.75 per cent PHENOL IN ORIGINAL ACIDS(calculated). . . . . . . . . . . . . . 32.2 per cent
.......................
{
.......................
T h e method requires a b o u t t w o days t o complete a test b u t several can be r u n simultaneously. T h e keynote of success i n this work is extremely careful a n d accurate attention t o t h e details of manipulation. This test has been in use i n our laboratories since t h e early p a r t of 1916, a n d has given very satisfactory results. RESEARCH DEPARTMENT, THE BARRETTCOMPANY 17 BATTERYPLACE,NEN YORKCITY
A NOTE ON SILICON-COATED METAL By W, E. VAUTER Received February 10, 1917
T h e resistance of silicon t o t h e corrosive action of acids a n d alkalies is t a k e n advantage of i n chemical industry b y using apparatus constructed of iron which contains a large percentage of silicon. However, t h e high silicon castings h a v e small tensile or compressive strength a n d breakage is high. It was therefore thought t h a t , if iron could be satisfactorily coated with silicon, a great saving could be effected. Coating iron b y dipping into molten silicon is unsatisfactory, since t h e melting points of t h e metals are similar a n d iron is soluble in fused silicon.
V O ~9, . SO.6
T h e object of a s t u d y made b y t h e author was t o investigate a process for coating a metal, preferably iron, with silicon, so t h a t t h e non-resisting metal would be amply protected from a n y corrosive chemical, a n d a t t h e same time s t a n d u p under severe handling, without injury t o t h e object or t h e protective coating. Samples of iron were heated t o temperatures of l o o to 600' C. i n a n atmosphere of silicon hydride,' in order t o ascertain whether t h e gas would decompose a n d form a coating of silicon upon t h e surface of t h e iron. E X P E R I Y E NT A L
I-Iron wire was heated t o j50' C. in a current of d r y silicon hydride for one hour. Small patches of silicon formed over t h e surface of t h e wire, b u t when t h e sample was placed i n a normal solution of sodium chloride, corrosion immediately s t a r t e d where no silicon was present, totally undermining t h e silicon coating after t w o weeks' immersion. 2-A repetition of Experiment I . I n this experiment t h e silicon did not appear t o be undermined; t h e coating of silicon remained after t w o weeks' immersion, although corrosion h a d taken place rapidly a t all other places. 3-This sample was heated t o joo' C. for t w o hours. A t h i n film of silicon was deposited on t h e wire a n d t h e wire became badly pitted where there was no coating of silicon. T h e silicon coat was intact after t w o weeks' immersion. 4-This sample was heated for 3l/2 hrs. a t 550' C. Very little silicon adhered t o t h e wire, a n d t h a t which deposited was in scales a n d could easily be removed. j-This sample was first pickled i n acid a n d t h e n heated in a current of silicon hydride a t j j o ' C. for 2 hrs. T h e resulting coating was smooth a n d uniform in color, a n d t h e treated iron remained i n salt solution four days before a n y corrosion was noticed; this was a t t h e end where t h e wire h a d been cut a n d h a d no silicon protection. 6-The sample was first heated t o 7 0 0 ' C. a n d t h e n allowed t o cool t o 550' C. before exposing t o t h e gas. While a n excellent coat was obtained, which stood up well i n t h e salt solution, no advantage i n preheating could be observed. ;-This sample, after running t w o hours at j jo' C., was further heated for j minutes a t 700' C. Ten days' immersion in salt solution completely removed t h e coat. I t was expected t h a t t h e silicon would a t t a c h itself more firmly t o t h e iron b y t h e heat t r e a t ment, b u t t h e after-heating probably broke t h e coat a t some place a n d allowed corrosion t o set in. 8-An exact duplicate of Experiment 5 with similar results. 9--A piece of wire, which h a d been pickled, washed, dried a n d exposed t o t h e air for several hours, until 1 The silicon hydride used in these experlments was prepared by treating an alloy of magnesium and silicon with a dilute solution of hydrochloric acid. The evolved gas consisted of about 5 per cent of sllicon hydride and 95 per cent of hydrogen. The alloy was pcepared by intimately mlxtng one part of powdered silicon with two parts of powdered magnesium and heating the mixture for two hours a t 600° C. in an atmosphere of hydrogen This alloy has the composition approximately represented by the formula SiMgz.
T H E J O l7R X A L 0 F I S D C S T RI -4 L A A- D E S G I S E E RI XG CH E M I ST R E'
June. 1917
a film of oxide had formed, m,s treated as in Experiment j, b u t no silicon adhered t o t h e wire. IO--.% sample was heated at j joo C. for I O rnin. a n d t h e temperature was t h e n changed t o 700' C. for t h e same period. This alternation was prolonged I'/* hrs. Little silicon deposited upon t h e r i r e a n d t h a t which did h a d a tendency t o scale off. II--~ sample treated b y t h e method used in Experiment j w a s replaced in t h e t u b e a n d heated t o 700' C . . b u t t h e coat scaled. I?-This sample was heated j hours a t T j o ' C. Silicon deposited upon t h e wire, b u t a slight bending would break t h e coat a n d it could be peeled off with t h e fingers. T h e wire did not h e a t unifornily a n d t h a t portion which was maintained a t a lower temperature did not give this fracture effect. The iron under the scale was unchanged. which n - o d d indicate t h a t t h e silicon merely forms a shell o r e r t h e iron. Other metals, copper, nickel and aluminum, were also subjected t o xreatment] b u t no coating of a n y description was obtained. I t is interesting t o observe.that silicon will coat iron when applied b y this method, under proper conditions: b u t n o practical use can be looked for along this line. K h a t was desired was a n adherent, homogeneous deposit of silicon on iron; b u t t h e above experiments showed t h a t only a thin a n d fragile shell formed over t h e iron. I
1\IELLOK INSTITUTE O F INDUSTRIAL
RESEARCH
~ N I V E R S I T YO F P I T T S B U R G H
THE COMPOSITION OF MENHADEN OIL FATTY ACIDS' By
E. TWITCHELL
The object of this analysis was as much t o test t h e use of my melting-point method of determining f a t t y acid mixtures as t o investigate t h e t r u e composition of t h e f a t t y acids found in menhaden oil. In a previous paper2 I described a method of determining t h e composition of mixtures of solid f a t t y acids. which consisted in adding a certain proportion of the mixture t o be analyzed t o a solvent consisting of a pure f a t t y acid of t h e kind t o be determined, t h e n finding t h e melting point a n d noting horn much t h e original melting point of the solvent h a d been depressed. This depression was caused b y all t h e acids in t h e mixture except t h e one sought, 1%-hich:being identical with t h e solvent, would have no effect on i t Assunling t h a t t h e other acids, singly or in mixture, produced a lowering of t h e melting point of t h e solvent proportional t o their total concentration a n d independent of t h e kind of acid, it was a simple calculation t o find t h e amount of these other acids a n d , b y difference. t h a t of t h e one sought. The assumption t h a t t h e lonrering of the melting point of the sox-lent acid is proportional t o t h e percentage of foreign acids is very nearly true in most cases u p t o 2 0 per cent, though, if t h e solvent is a n acid of unusually low melting point as compared with t h e dissolved acid, as for instance, behenic dissolved i Read a t the 21 l t h regular meeting of the Cincinnati Section American Chemical Society, March 28, 191;. THISJ O U R N A L 6 (1914), 564.
j81
in myristic acid, t h e melting-point curve beyond I O per cent of t h e dissolved acid is no longer a straight line and t h e depression caused b y 20 per cent of this acid is abnormally great. I n such cases only I O per cent of t h e acid of higher melting point n-as used in t h e mixture. T h e assumption t h a t all acids produce t h e same lowering of melting point is for this purpose near enough t o t h e t r u t h where t h e more common fats and oils a i e concerned, t h e f a t t y acids of which do not differ greatly in molecular n-eight. I have generally t a k e n 4 ' as t h e lowering of melting point caused b y adding 20 parts of one f a t t y acid t o 80 parts of another considered as t h e solvent. However, where t h e acids are t o some extent knot?-n it will be more accurate t o take values determined for each f a t t y acid. X number of these values I shall give below. This as a n analytical method is limited t o f a t t y acids solid a t ordinary temperatures, b u t can be extended b y applying it t o t h e solid f a t t y acids obtained from liquid acids either b y t h e hydrogenation process or b y fusion with caustic potash. T h e hydrogenation process, b y t h e addition of hydrogen, coni-erts unsaturated f a t t y acids into saturated ones having t h e same number of carbon atoms; oleic, linolic, linolenic and clupanodonic acids are all converted into stearic acid. Fusion with caustic potash produces a decomposition of members of t h e oleic. series b y which t h e principal product is a saturated f a t t y acid h a r i n g two less atoms of carbon; oleic acid is converted into palmitic acid, erucic into arachidic, etc. Linolic acid, with t w o double linkages, is converted into myristic acid a n d it may be assumed t h a t all acids of t h e linolic series on fusion with caustic potash yield a saturated acid with four less carbon atoms. As t o t h e action of caustic potash on t h e still more unsaturated acids, so far as I know, no experiments have been made, though it has been assumed t h a t acids with three double linkages (linolenic acid) would yield a saturated acid of six less carbon atoms a n d those having four double linkages (clupanodonic acid) would yield a saturated acid having eight less carbon atoms. I t is easily seen what an aid this power of converting liquid acids into solid acids according t o definite laws can be toward arriving a t t h e composition of a f a t t y acid mixture; and in m y previous paper I made use of t h e hydrogenation process. I n t h a t paper I gave results of m y analysis of menhaden oil f a t t y acids as follows: Per cent 22.7 . . , . . . . . . . . . 11.8 with 16 carbon a t o m s . . . , . . . , . . . S o n e 26.7 with 18 carbon a t o m s . . . , . . , . . , . 20.2 with 2 2 carbon a t o m s . . . . . . , 18.6 acids., , , , , . . . , , , . . . . . . . .
.....
Unsaturated acids Unsaturated acids Unsaturated acids Other unsaturated
__ loo
o
T h e vacancies in this analysis were due t o my not having t h e pure standard acids t o correspond with all of t h e f a t t y acids in t h e mixture. I had a t t h a t time only palmitic, stearic and behenic acids. I have since prepared myristic and arachidic acids, making t h e series of normal saturated f a t t y acids n-ith even num-
