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 X G 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-
582
T H E J O U R N A L OF I N D U S T R I A L A N D EXGINEERIXG C H E M I S T R Y
bers of carbon a t o m s complete between myristic a n d behenic acids inclusive. P R E P A R A T I O S O F U Y R I S T I C ACID
T h e f a t t y acids of nutmeg b u t t e r were repeatedly crystallized, first from petroleum ether a n d t h e n from 76 per cent alcohol. I n all there were thirteen crystallizations, t h e last few of which scarcely made a n y change in melting point or combining weight. T h e combining weight b y titration with alkali was 2 2 8 . j (theory 2 2 8 ) . T h e melting point was 5 3 . 7 6 " .
Vol. 9 , NO.6
likely be found in t h e first fraction. T o further concentrate i t , a portion of this fraction was dissolved i n alcohol, partially precipitated with lead acetate a n d filtered. T h e f a t t y acids were separated from t h e filtrate a n d melted i n t h e proportion of 20 parts with 80 parts of myristic acid: The m. p. of this mixture w a s . . . . . . . . . . . . . . . 51 .60° T h a t of uure mvristic acid i s . . . . . . . . . . . . . . . . . 53.76O T h e lowering of the m. p. was therefore.. . . . . . . The lowering of the m. p. of myristic acid by 20 per cent of palmitic acid is. . . . . . . . . . . . . . . . . The percentage of myristic acid in the fatty acids under examination is therefore: 100 X ( 4 . 5 3 - 2 . 1 6 ) i 4 . 5 3 = ......................
2.16O 4.53O 52.3
Percent,
P R E P A R A T I O S O F A R A C H I D I C ACID
S o f a t could be found t h a t contained a n y considerable q u a n t i t y of this acid; b u t rape oil contains erucic acid, which on fusion with caustic potash, should yield arachidic acid. T h e f a t t y acids of rape oil were fused for 6 hrs. with caustic potash a t 300' C. At t h e end of this time t h e liberation of hydrogen h a d ceased. T h e f a t t y acids were separated from t h e other products of t h e fusion, a n d , as arachidic acid seemed t o be t h e acid of highest melting point i n t h e mixture, i t was a simple matter t o separate i t from t h e rest a n d t o purify i t b y simple crystallization from petroleum ether a n d 90 per cent alcohol. Eight crystallizations gave a n acid having a combining weight of 3 I z (the theoretical) a n d a melting point of 74.78'. T h e following table gives t h e melting points of mixtures in pairs of all t h e series of five acids before mentioned, 80 p a r t s being t a k e n of one, considered t h e solvent, a n d mixed with 2 0 p a r t s of each of t h e others. T h e method of determining t h e melting point was about a s described i n m y previous paper. Correction was always made for t h e s t e m of t h e thermometer which extended above t h e bath.
Behenic acid. . . . . . . . . . . . Arachidic acid.. . . . . . . . . . Stearic acid.. . . . . . . . . . . . Palmitic acid.. . . . . . . . . . . Myristic acid.. . . . . . . . . . .
i9.99 74.78 69.30 62.37 53.76
...
71.17
...
._.
...
3.61 4.02* 3.68*
which clearly establishes t h e presence of myristic acid i n t h e hydrogenated oil. Whether i t was present i n t h e original oil or was formed from a n unsaturated acid b y hydrogenation Rill be determined later. T h e value 4. j 3 O ( t h e depression caused b y palmitic acid as given in t h e table) was used in this calculation because i t was practically certain t h a t t h e acids other t h a n myristic in t h e substance were chiefly palmitic. For more accurate quantitative results, another mixture'should be made as described i n m y previous paper; t h a t is, using so much of t h e substance t o be examined t h a t t h e lowering of melting point is a b o u t 4 O. A R A C H I D I C ACID IS H Y D R O G E N A T E D M E N H A D E N O I L
Fractions I j a n d 16 of this same distillate h a d a n average combining weight of 308.j a n d were t h e most likely t o contain arachidic acid. T h e y were united a n d crystallized twice from 90 per cent alcohol at I j " C. T h e mean combining weight of t h e crystals was 3 2 4 . I n my previous work i t h a d been shown t h a t behenic acid (molecular weight 340) was present i n t h e hydrogenated oil. It would almost certainly be in this fraction. I t remained t o determine whether t h e
76.42
3.57
...
7.5.81 71.05
4.18 3.73
65:i4
3.96 3.88* 3.62'
...
75.45 70.79 65.08
4.54 3.99 4.22
58:i6 ,..
4.21 4.42*
49:i3
4:j2
...
75.31 70.49 64.91 57.77
...
4.68 4.29 4.39 4.60
..
*On account of the relatively high melting point of the dissolved acid the mixture was made with 90 parts solvent plus 10 parts dissolved acids. The lowering of melting point multiplied by 2 gives a n imaginary value for the 80 -!- 20 mixture.
T h e figures given in this table are not quite t o be considered as final, as I a m not yet satisfied with t h e accuracy of m y method of determining melting points a n d hope t o improve it. M Y R I S T I C ACID Ih- H Y D R O G E S A T E D M E N H A D E X O I L
I n t h e course of my previous work on menhaden oil
a fractional distillation h a d been made of t h e f a t t y acids separated from t h e hydrogenated oil. There were twenty-one fractions i n all. I n this distillate were found behenic, stearic a n d palmitic acids. T h e presence of arachidic a n d myristic acid seemed probable, b u t having neither of these acids i n t h e pure s t a t e I could n o t a t t h a t time establish their presence i n a n y of t h e fractions. If a n y myristic acid were present i t would very
reduction in combining weight was due t o arachidic acid, 20 parts of the crystals melted with 80 parts of arachidic acid had a m. p. o f . , . . . . . . . . . . . . . . . 72.95 Arachidic acid has a m. p. o f . , . . . . . . . . . . . . . . . . . 74.78
-
1.83 The lowering of the m. p . was therefore., . . . . . . . T h e lowering of the m. p. of arachidic acid by 2 0 3.61 per cent of behenic acid i s . , . . . . . . . . . . . . . . . . . T h e percentage of arachidic acid in the crystals is therefore 100 X (3.61 1.83)/3.61 = . . . . . . . 4 9 . 3 Per cent,
-
which establishes t h e presence of arachidic acid i n t h e hydrogenated oil. As a matter of interest a test was made for behenic acid i n t h e same fraction. 20 parts melted with 80 parts of behenic acid caused a lowering of m. p. of the latter of. . . . T h e percentage of behenic acid in the substance is therefore 100 X (3.57- 1.96)/3.57 =..
...
1.96' 45.1 Per cent
T h e percentage of arachidic acid i n t h e t o t a l f a t t y
June, 1 9 1 7
T H E J O U R h - A L O F I h - D U S T R I A L A;\-D E L 3 v G I S E E R I S G C H E M I S T R Y
acids of t h e hydrogenated oil, not distilled, was determined as follows: 20 parts were melted with 80 parts of arachidic acid. T h e mixture had a m. p. o f , . . . . . . . . . . . 71.67 T h e m. p. of arachidic acid i s . , . . . . . . . . . . . . . . . . 74.78
.
__
T h e lowering of m. p. is therefore. . . . . . . . . . . . . . 3.11 T h e lowering of the m. p. of arachidic acid by the other acids in the mixture is taken a s . . . . . . . . . 4 . 0 0 T h e percentage of arachidic acid is therefore 100 X (4.00--3.01)/4.00 22.2
...............
which is either in t h e original oil or has been produced b y hydrogenation. T H E SOLID FATTY ACIDS O F M E N f i A D E S OIL
These were separated from t h e liquid acids b y t h e method described in my previous paper. i l b o u t 31 per cent were obtained, having, however, an iodine value of 9.44, equivalent t o 10.5 per cent of oleic acid, which, for t h e purposes of this calculation, I shall assume it t o be. T h e menhaden oil which I used for this work was unfortunately not t h e same as t h a t I h a d used i n m y former work. It was not so fresh a n d contained more free f a t t y acids t h a n I could have wished. This m a y account for t h e rather high iodine value of t h e separated solid acids. 20 parts of these solid fatty acids melted with 80 parts of myristic acid, had a m. p. of. . . . . . . . . 5 0 . 5 7 Myristic acid has a m. p. o f . , . . . . . . . . . . . . . . . . . 53. 76
.............
T h e lowering of in. p. is therefore. 3.19 The lowering of the melting point of myristic acid by 20 per cent of palmitic acid i s . . . . . . . . . . . . . 4.53 The percentage of myristic acid in the solid fatty = 29.6 acids is therefore 100 X (4.53-3.19)/4.53
As a confirmation of this result a n d t o leave no d o u b t t h a t myristic acid was really present, t h e above solid f a t t y acids were dissolved i n alcohol a n d enough lead acetate added t o precipitate about one-half. T h e f a t t y acids separated f r o m t h e filtrate, tested as above, gave 4 j . 9 per cent oE myristic acid. 20 parts of the same solid fatty acids melted with 80 parts of arachidic acid had a m. p. of. . . . . . 70 .ST Arachidic acid has a m. p. of.. . . . . . . . . . . . . . . . . . 74.78
The lowering of m. p. is therefore. . . . . . . . . . . . . . 4.21 The lowering of the m. p . of arachidic acid by 20 per cent of palmitic acid is. . . . . . . . . . . . . . . . . . 3 . 9 9 T h e percentage of arachidic acid is therefore 100 X (3.99-4.21)/3.99 = -5.5 per cent = None
I n t h e s a m e y a y t h e percentage of palmitic acid in t h e solid f a t t y acids was found t o be 5 2 . 9 per cent, a n d of stearic acid 5 . 7 per cent, a n d as t h e oleic acid, from t h e iodine value, was 10.5 per cent, t h e composition of t h e solid acids as separated, is: Myristic acid., ............................... Palmitic acid.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stearic acid., ................................. Arachidic acid ..................... .... Oleic acid, . . .
Per cent 29.6 52.9 5.7 None 10.5
98.i
-4s t h e menhaden oil f a t t y acids contained 31 per cent of acids of t h e above composition, t h e a m o u n t of myristic acid i n t h e menhaden oil f a t t y acids is 29.6 X 0.31 = 9.2 per cent a n d of stearic acid j . 7 X 0.31 = 1.8 per cent,. I n m y previous paper I expressed a d o u b t a s t o whether there was a n y stearic acid in the mixture, though t h e tests gave small positive figures. This d o u b t might still exist, a n d t o decide this point a fractional precipitation was made of t h e f a t t y acids of menhaden oil dissolved in alcohol, using only enough
583
lead acetate t o precipitate about 2 per cent of f a t t y acids. This precipitate, on decomposing, yielded f a t t y acids testing 26. j per cent of stearic acid. There can be no doubt of t h e presence of stearic acid in t h e original oil. G E S E R A L RESULTS
Having found myristic acid in both t h e original a n d t h e hydrogenated f a t t y acids i n equal amounts, it was not produced by hydrogenation. On t h e other hand arachidic acid was found only in t h e hydrogenated a n d not i n t h e original f a t t y acids. I t was therefore produced b y t h e addition of hydrogen t o a n unsaturated acid with 20 atoms of carbon. T h e composition of menhaden oil f a t t y acids given in m y paper of July 1914, can now be filled out as follows : Palmitic a c i d , , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Myristic acid.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stearic acid.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Unsaturated acids with 16 carbon atoms.. . . . . . . . Unsaturated acids with 18 carbon atoms = 26.7 less 1.8 per cent stearic acid = Unsaturated acids with 20 carbon atoms.. . . . . . . . Unsaturated acids with 22 carbon atoms.. . . . . . . .
.........
Per cent 22.7 9.2 1.8 None 24.9 22.2 20.2
As t o t h e series t o which t h e unsaturated f a t t y acids with t h e different numbers of carbon atoms belong, t h e method of fusion with caustic potash above mentioned will give some information. On fusing t h e menhaden oil f a t t y acids with caustic potash a n d separating t h e higher f a t t y acids from t h e product, a mixture was obtained which would not crystallize from 90 per cent alcohol except a t very low temperatures, a n d this already indicated t h a t it contained no arachidic acid. I t was crystallized from 76 per cent alcohol. 20 parts of the crystals melted with 80 parts of arachidic acid had a m. p. o f , , . . . . . . . . . . . . . . . 7 1 , 0 4 74.78 The m. p. of arachidic acid i s . .
................
The lowering of m. p. was therefore.. . . . . . . . . . . . The lowering of the m. p. of arachidic acid by 20 per cent of stearic and palmitic acids, is., . . . . . T h e percentage of arachidic acid is therefore 100 X ( 3 . 8 6 - 3 , 7 4 ) / 3 . 8 6 = ...............
3.i4
3.86 3.2
As this was in a small fraction which should contain all of t h e arachidic acid present, t h e a m o u n t in t h e total product of t h e fusion would be very small if, indeed, it can be inferred from t h e above low figure t h a t its presence has been proved at all. F r o m this i t can be concluded t h a t t h e unsaturated acid with 2 2 carbon atoms found in menhaden oil a n d which, like erucic acid, is converted b y hydrogenation into behenic acid, is nevertheless not erucic acid, since on fusion with caustic potash it is not con\-erted into arachidic acid. It is probably a more unsaturated acid which is converted into stearic or palmitic acid b y t h e fusion. T h e above fraction was also tested for palmitic and stearic acid a n d found t o contain: Palmitic acid, 73.6 per cent; stearic acid, 23.6 per cent. T h e factors for lowering of melting point given in t h e table, although still somewhat uncertain, cannot be far enough from t h e t r u e ones t o affect t h e results very seriously. E v e n if t h e average value, 4O, for t h e depression caused b y mixing 2 0 parts of one acid with So of another h a d been used in m y calculations, t h e
584
T H E J O C R - V A L O F I - V D C S T R I A L A4VD ENGI+VEERILVG C H E M I S T R Y
general conclusions as t o t h e composition of menhaden oil would not have been changed. As t o t h e usefulness of this method, I know of no other way of determining t h e composition of a mixt u r e of solid f a t t y acids of more t h a n two constituents, especially where only a small q u a n t i t y is available. E v e n with large quantities, though it might be possible b y means of numerous fractional precipitations or distillations t o separate some of each of t h e constituents i n a pure s t a t e , a quantitative result can never be obtained i n this way. WYOMING, OHIO
NOTE ON THE DETERMINATION OF STRONTIUM AND LITHIUM IN WATER By S. D. AVERITT Received December 13, 1916
There are probably no determinations i n water analysis which on t h e whole require more time a n d work t h a n those of strontium a n d lithium. Several years ago while cobperating with t h e Referee on Water -1nalysis for t h e Association of Official Agricultural Chemists. t h e methods which are now official for strontium a n d lithium were tested. T h e great a m o u n t of time a n d work required for these determinations led t h e writer somewhat later t o inrestigate t h e accuracy of indirect methods which were sound i n theory a n d which, with careful work, must prove accurate provided there was a really determinable a m o u n t of strontium or lithium present; t h a t is, a n a m o u n t t h a t would not be too seriously affected b y t h e experimental error unavoidable in t h e most careful work. This investigation led t o t h e conclusion t h a t t h e indirect methods employed were as accurate as t h e official methods a n d t h e time a n d labor saved was a m a t t e r of considerable importance. I t is self-evident t h a t pure preciptates a n d careful work are necessary for indirect methods, t h e lack of which has undoubtedly h a d much t o do with t h e u n favorable opinion many chemists entertain relative t o them. I t is believed t h a t a brief statement of t h e methods will b e of general interest t o water analysts a n d others who have occasion t o determine strontium a n d lithium, as t h e y differ materially from other indirect methods t h a t have been proposed, a t least i n their application t o t h e separation of calcium a n d strontium a n d t h e extent t o which t h e y are carried in t h e separation of t h e alkalies. I n t h e brief statement which follows, no details of procedure will be given as t h e y should be perfectly familiar t o a n y analyst of reasonable experience. The official method (Stromeyer-Rose) for t h e determination of strontium begins with t h e weighed oxides of calcium a n d strontium (CaO a n d SrO). These are dissolved i n nitric acid a n d brought t o dryness, t h e separation of strontium depending upon t h e insolubility of strontium nitrate in alcohol-ether mixture. T h e writer’s method is as follows: Dissolve t h e weighed oxides in hydrochloric acid a n d precipitate again as oxalates as i n t h e first case; filter, wash, dis-
Vol. 9, No. 6
solve in sulfuric acid a n d t i t r a t e with standard K M n O a , noting t h e exact volume of K h I n 0 4 required. If T i ’ = weight of CaO a n d SrO. 0 = t o t a l oxygen i n CaO a n d SrO (found b y t h e titration with K A l n 0 4 ) . X = 0 in CaO. Y = 0 in SrO. T h e n ,Y E’ = 0 (1) and 3.j044X 6.4769Y = T I 7 (2) Solving for Y ,determine SrO (6.4769Y) t h e n W - SrO = CaO. When t h e value of E‘ is found, in order t o get 6.4 7 6 9SrO a constant factor occurs which is 6.4769 - 3.5044 or 2 . 1 j 9 . Consequently i t is not necessary t o solve these equations i n order t o get t h e weight of SrO, which is obtained as follows: - CaO equivalent of K h f n 0 4 titration) 2 . 1 7 9 = SrO. (3) I n order t o test t h e accuracy of t h e above method, pure C a C 0 3 equivalent to 0.9954 g. CaO a n d S r C 0 3 equivalent t o 0.1000 SrO were dissolved i n hydrochloric acid a n d made u p t o 500 cc.; 50 cc. aliquots equivalent t o 0.09954 g. CaO a n d 0.0100 g. SrO were used, giving t h e results shown in Table I.
+
+
(w
TABLEI-DETERMINATIONOF STRONTIUM (RESULTSI N GRAMS) Expt. A-0. 1
2 3
...... . . .
-CaO Present 0 1095 0.1095
0.1095 4. 0.1095 5(a) 0.1095 ( a ) Precipitated in
........ .... ...
+ SrOFound
0.1095 0.1096 0.1096 0.1096 0.1097 presence of
CaO Equivalent -SrO----. of KMnOd Present 0.1048 0.0100 0.1052 0.0100 0 1049 0.0100 0 1051 0.0100 0 1052 0.0100 magnesium chloride.
Found 0.0102 0,0096 0.0102 0.0098 0.0099
T h e oxalates were washed with a l/2 per cent solution of ammonium oxalate i n all cases. Those which were t o be t i t r a t e d were finally washed with 1 5 cc. of cold water i n 5 - c ~ portions . dropped from a pipette around t h e t o p of t h e filter fast enough t o cover t h e precipitate. letting t h e filter r u n dry between each washing. This a m o u n t of washing with water is sufficient for aliquots containing approximately 0.0300 g. of oxides a n d it is not advisable t o have much larger aliquots for titration nor t o use more water i n washing, otherwise strontium oxalate will be dissolved. If t h e double oxides weigh more t h a n 0.0500 g., aliquots should b e t a k e n for t h e K M n 0 4 titration. T h e K M n O l should not be stronger t h a n N/Io. T h e Official Method for t h e determination of lithium (Gooch) begins with t h e weighed chlorides (NaC1, KC1 a n d LiC1) a n d depends upon t h e insolubility of sodium and potassium chloride i n absolute amyl alcohol. T h e writer’s method is t o make t h e solution in water of t h e weighed chlorides of sodium, potassium a n d lithium u p t o convenient volume. T a k e a n aliquot for t h e determination of K from which KC1 a n d t h e C1 in t h e same becomes known. Another aliquot is t i t r a t e d with s t a n d a r d AgN03 from which t h e total C1 is obtained. If T.T’ = weight of S a C l KC1 LiC1. C = weight of t o t a l chlorine (as found b y titration with AgNO3). CZ in NaCl LiCl = C - CZ i n KC1. X = Cl i n XaC1 a n d Y = CZ in LiC1.
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