V O L U M E 23, NO. 12, D E C E M B E R 1 9 5 1

ncltlition o f starch near the end, until the pale brown color suddenly changes to milky white. The mixture may be agitated during t,he titration t>>- alternately applying suction and pressure with the mouth through a rutiher tube attached to the open end of the spray trap while the latter is fitt,ed t'o the alisoher.

CA XU LATION S

The thiol content may l)e c:ilculated in trrnir o f sulfur by n i w r i y o f the follo\ving equatioAi:

s = 0.05609(25 ~ - T')(460 + t ) H - P

\ ~ I I I ~ I Y ~ S = thiol sulfur rontent, gr:iina of sulfur 1x1' 100 culiic: feet of gas saturated Jvith n-atcr v:ipi>r a t 60" F and 30.0 iric.hw crf niei'cwry

1- = volunie of 0.1 .\ thiosulf:itt, i.equirri1, nil. t = tcmprratui~c < , f outlet gas, O F. H = t)aroniet rio 1)rc.w11'e, inrhes of niercw p = v : i l i o i ' ~ I I ~ I W ~ I ~ < ~ of n-ater at t o F., iricmh

.I iioniographir chart for cnlculating the thiol sulfur (,ontent \\-lii~i all st:indard rcxgents are exactly 0.1 S i s given in Figure 2. Tlic. (ahart is Iiased on the v:ilue 1.032 for p , which is t h r vapor ti.iiPion of water a t 80" F. 1-dues of thiol content o1)tainc.d from the chart :it other ga.; teniper:itur(Js normally encount isred art: sufficic~ntly accuratii for most purpose^, as variations i l l p :it room temperaturos (mwt- rc~lativel:- small errors in thiol i m t m t .

1 hy 1:iying :I straight-edge betn-een the, oliwrvid LIW lint1 gas temperature>, noting \\-here it i~rossc~s

thr refeiwiri~ line, and rstrnding the edge across the point on the ri~ftwnce line arid the volume of thiosulfate uwd in the, titi,:ition to thc thiol contrsnt ; ~ x i i .

1779

DISCUSSION

Ihpl jcatr a n a l ~ x ~ f rom the sanic sample bonih provitfrd with tl\-o [--tubes in parallel, onr of copper :ind one of glaaa, l cd ing

to individual absorbers and nietcra, produced identical rcwlta, showing that the samples are not partially "sweetened" (cxon- verpion of thiols t o disulfides) by cxontact with the coppt'r tul)r. It, was found that accuracy could not be improved by u*ing nioi'e dilute than 0.1 S cupric acetate reagent. Reaction of tlir, cupi ic ion with the thiols !vas incomplete i f less than 25 nil. of rc.:igent ivere usi~d in the ukisorlier, prohably liecause of inuficmieiit w n - tart tinir, :is only a rcJlatively p m : i l l fraction of this i(.:ig(,iit is consunird by the. thiols. I-sr of hydi,ochloric and Fuliut ic. :ic,itis in the ahsorhei. rwgrnt initrad of acrtic proved to Iw uiixitis- factor!.. The c'xact r:ingc of pH value rrquired for gc~tr(l t iw l t s \vas not deterniincd, but indications are that it should I K :illout 3.0 or 3.5 2nd not higher than 4.0. The cupric ac,i.t:itij-:ic.c,tic acid huffer prc~parc~l as drscribed consistentlj- producrd t l q i i ~ n i l -

nlilt, rrsults aiid pH rc3quirenients were not explored fu1.t lirr - I ( ~ t y l r n e and its homologs aril normally not prewiit i t 1 c.itlier

natural or refinrry gases. This highly unsaturatd g:i- w:+rts \vith cuprous ions only in aninioniacal solution. Furt I ~ I ~ I ~ ~ I I I ~ I ~ , ;ic~c~tylwie is lilirratrd from acrtylides by ncid:: (5 :. lio~ice,

n if prcwmt, n.oultl not i.v:+c.t with the. : i c . i t l c~)lil)er iwigcwt i n thv a l i sorhr .

LITERATURE CITED

(1) Aut. ( A . s .J., 162, To. 0 (194.5). '21 . \in. Soc. Testiiig lIatei.iaIs, "=\ST11 Standard>." 3Iethod

r:l) . - \ i d t i , I t . K . , I-'et,cy. L. I:., ant1 1,:srhet.. E. E.. fAf.,. 26, S o . 5,

(4) Hakewill. H.. aiid Rueck. E. 31.. P,.or.. - 4 ~ . Grta -4 (1946).

1.5, liii-hter. Victoi. m r i , "(kgaiiic ('heinistly,' ' 31d et1 , 1.01, 1, .\nici~ii;aii Photo Offset Reyl.int. l i p 110-11, S e n - Tior 1;. \-III rle- ~iiaii I'iihlishiiig r o . , 1944.

\ t i ) Shaw, .J. 1.. I s n . Esc;. ('HEM., ( 7 ) IVhite, D. L., aiid Reichnr.dt. F

RECEIVED .4pril 19,1951.

D 90-4iT.

47- 5:3 (1950).

\I . . En., 12, 668 11940l. , G u s , 25, No. G , 38-9 (1049).

Determination o f Small Amounts of Dimethylamine in Technical Methylamines

Simple Method for Separation of Dimethylamine from Monomethylamine

EDWARD L. STiNLEY, I I i R R Y BiU\.I, 4 Y D JESSIE L. GOVE Rohm and Huus Co., Bridesburg, Philadelphia, P a .

HI< catalytic vapor phase reaction of methanol arid am- T nionia produces a complex mixt,urr of water, monomethyl- amine, dimethylaminr, trimethylamine, ammonia, arid methanol. The monomethylamine and trimethylamine separated from this mixture usually contain less than 1 dimethylamine, but m:iy contain as much as 3%. A precise, accurate, and rapid method for the determination of dimethylamine in the anhydrous amines and in their aqueous solutions was desired.

In the procedures used generally for the determination of di- methylamine in methylamine mistures, the monoinethylamiiie is tlecomposd with nitrous acid and the resulting dimethylnitroso- amine and unrracted trimethylamine are steam-distilled into staiidard acid ( I O ) . The excess of the acid is titrated with alkali and the nitrosoamine is then reduced with zinc. Suhsequent titration of the alkaline distillate of the reaction mixture yields the total secondary and tertiary base and, from this, the diniethyl- amine is calculated by difference. It is necessary to apply Fmpirical corrections and the procedure is unsatisfactory for small amounts of dimethylamine because of the accuniulatioil of c'rrors on the diniethyl:iniine.

One method with which some success lias been ol)tained in this laboratory has heen reported (9). However, this procedure does not determine dimethylamine directly and some interfri,cnce in thr prc'sence of nioriomethylainiiie has been noted.

Srvwal procedurc~s fot, the direct determination of tliniethyl- :imine have been described (2 , 4, 7 , 8). The polarogr:iphic. pro- cedure of Smales and JVilson was investigated, hut did not give satisfactory results in this laboratory. English has ingeniously overconic m n i ~ of the shortconiings of thr Smales and \\.ikon p i~oc~dure , but reports that his method is not suitalilr for the determination of sinall amounts of dimethylamine. Iiatcher and \Toroshiloir:i titmted the dimethyldithiocnrbaiiiate salt of the amine with a cupric sulfate solution. This niethod TI-ould be applicahlr to the determination of large amounts of tlimcthyl- :iniinr in the ahsence of moiiomethylariiine; triniet h:,lainine would presumably not interfere. The colorimetric procedure of Dowlen, originally d loped for the determination of small amounts of dimethylamine in biological fluids, appearrtl to offer thr greatest promise and was intensivrly investigated.

T h e Doivden procedure is b a d on the forniatioti of the

1780

amber-colored cupric dimethyldithiocarbamate in ammoniacal solution :

A N A L Y T I C A L C H E M I S T R Y

below. Typical absorption curves obtained with dimethyl- amine, using the Beckman spectrophotometer, are illustrated in Figure 2. The maximum absorption for dimethylamine was obtained a t 434 mp with the Beckman instrument and a t 440 mp with the Coleman spectrophotometer, probably because of the larger band width of the latter instrument. The calibration curve obeys the Beer-Lambert law only over small ranges of con- centration and the slope of the y v e differs for the two instru- ments.

Maximum intensity of color was obtained when the flasks were heated in the water bath for 3 minutes; the absorbancy obtained is not affected if the heating period is extended to 10 minutes. The absorbancy of the colored complex in the benzene solution, after the benzene layer had been decanted from the other reagents, was found to be constant under labora-

Stability of Color.

s 2(CH3)zXCSNH( + C U + + + [ ( C H ~ ) J C S ] ~ C U J + 2NH4'

II I/ s s

The cupric salt is then extracted with benzene and determined in a visual colorimeter. Dowden's data indicated that the pro- cedure would be applicable to technical trimethylamine and this was found to be the case. However, the procedure failed in the presence of large amounts of monomethylamine. In this labora- tory the interference of methanol, monomethylamine, and tri- methylamine was studied and the effect of time and temperature on the stability of the colored complex was investigated. A spectrophotometric adaptation of the colorimetric procedure and a method of removing the interfering monomethylamine were developed.

REAGENTS AND APPARATUS

Unless otherwise indicatcd, all reagents were C.P. or reagent grade.

Acetic Acid Solution. Seventy-five milliliters of glacial acetic acid were diluted to 2.50 ml. with distilled water.

Amqoniacal Copper Solution. Fifty grams of ammonium acetate and 0.5 gram of cupric sulfate (CuS04.5HzO) were dis- solved in 75 ml. of water and transferred to a 250-ml. volumetric flask. To this was added a solution of 25 grams of sodium hydroxide in 50 ml. of water and 50 ml. of ammonium hydroxide (specific gravity 0.90). The solution was then made to volume with distilled water.

Benzene, technical grade, redistilled. Carbon Disulfide Solution, 5y0 by volume, in benzene. Chloroform, anhydrous. Fresh chloroform, as well as re-

covered reagent, was distilled through a short, packed column and the first and last 1Oyo of. distillate were rejected.

Dimethylamine Salt Solutions were prepared by neutralizing Rohm and Haas 407, dimethylamine, containing less than 0.5% of total impurities, with standard hydrochloric or sulfuric acids and diluting to the desired concentration.

Hydrochloric Acid, standard solution, 2 N . Methyl Red Indicator, 0.1 Yo aqueous. Monomethylamine Hydrochloride. The ammonia was re-

moved from Rohm and Haas anhydrous amine as described in an earlier paper ( 5 ) and the amine was distilled into concen- trated hydrochloric acid. After the water had been evaporated, the salt was recrystallized three times from ethyl alcohol, washed with hot anhydrous chloroform, and recrystallized from alcohol. The hydrochloride was dried a t 110' e. and stored in glass- stoppered bottles.

Monomethylamine and Trimethylamine Salt Solutions. Standard hydrochloride and sulfate solutions were prepared indirectly from the purified amine hydrochlorides by distilling with 10 N sodium hydroxide in a Kjeldahl distillation assembly. The volatilized amines were absorbed in standard sulfuric or hydrochloric acid until the diqtillate solutions were just alkaline to methyl red; the solutions were then neutralized with the appropriate standard acid and diluted t o the desired concentra- tion.

Sulfuric Acid, standard solution, 5 N . Sulfuric Acid, standard solution, 0.5 N . Trimethylamine Hydrochloride, obtained as described above

for monomethylamine, was crystallized from ethyl alcohol and then three times from chloroform. The salt obtained after dry- ing at 110" C. was found to be free of dimethylamine by the procedure descrihed in this paper.

Distillation Assembly consisted of a 125-m1., $24/40 Erlenmeyer flask in which a water trap (Figure 1) was inserted. The riser of the water trap was lagged with asbestos cord. A reflux con- denser was attached to the top of the trap.

Water Bath, 43' to 48" C. A pan of water heated on an elec- tric hot plate controlled by a rheostat was satisfactory.

Spectrophotometer. Both the Beckman Model DL and the Coleman Model 11 spectrophotometers were used.

EXPERIMENTAL

Determination of Dimethylamine. The method used for the development of the dimethylamine color is described in detail

Figure 1. Apparatus for Separation of Dimethyl- amine and Monomethyl-

amine

tory conditions for a t least 1 hour. After the benzene solu- tion had stood overnight, an increase in absorbancy of a p proximately 3% relative was noted.

Interferences. No interfer- ence with the determination of dimethylamine was noted when 1% of methanol was added to synthetic trimethyl- amine mixtures containing 1 % each of monomethylamine and d i m e t h y l a m i n e . T h e a b - sorbancy produced by 14.8 mg. of pure trimethylamine (hy- drochloride), a p p r o x i m a t e l y twice the amount usually taken for analysis, was found to be equal to the blank. Further- more, dimethylamine (sulfate) equal to 0.2 to 1.7% of the tri- m e t h y l a m i n e present, when added to 10-mg. amounts of trimethylamine, was recovered with an accuracy of 101 & 2.6%. It was concluded that trimethylamine does not in- t e r f e r e in t h i s p r o c e d u r e . When s imi la r e x p e r i m e n t s were made in the presence of 1.5% of monomethylamine (sulfate), added to the mixtures previously described, the di- methylamine was r e c o v e r e d with an accuracy of 100 =I= 1%. A white to pale brown precipitate of cupric mono- methyldithiocarbamate col- lected a t the interface between

the benzene and aqueous layers but did not interfere with the decantation of benzene. It was concluded that neither methanol nor monomethylamine, in concentrations likely to be encoun- tered in trimethylamine samples, would interfere with the deter- mination of dimethylamine.

However, in mixtures containing mainly monomethylamine, of the order of 2 to 10 mg. in the sample aliquot, positive errors in the determination of dimethylamine of the order of 10 to 35% relative were produced. It was concluded that monomethylamine samples could not be analyzed for dimethylamine without a preliminary separation of the dimethylamine.

The substitution of nickel for the copper cation did not result in a better separation of mono- and dimethylamines and the use of

Separation of Monomethylamine and Dimethylamine.

V O L U M E 23, NO. 12, D E C E M B E R 1 9 5 1 1781

In the manufacture of mono- and trimethylamines it is necessary to control the concentration of di- methylamine to rather low limits. Existing methods based on diazotization are unsatisfactory. The spec- trophotometric determination of dimethylamine as cupric dimethyldithiocarbamate has been found to be both accurate and convenient. The dimethyl- amine content of trimethylamine samples may be determined directly, but a preliminary separation of the dimethylamine is required for monomethyl- amine samples. This separation is accomplished

chloroform, ethyl ether, methyl hexyl ketone, and carbon disul- fide as solvents produced results similar to those with benzene. Aliphatic hydrocarbons failed to dissolve the copper complexes of either of the amines. A method for the precipitation of primary amines, used qualitatively by Duke (S ) , was also investigated, but quantitative recovery of the dimethylamine was not possible.

It is known that monomethylamine hydrochloride is relatively insoluble in chloroform while the dimethylamine and triniethyl- amine hydrochlorides are very soluble ( 1 ) . However, mono- methylamine could not be separated from dimethylamine by a direct extraction from an aqueous solution of a mixture of the hydrochlorides because of the high solubility of all the amine hydrochlorides in water. It mas believed that sufficient water could be removed from an aqueous aliquot by adding chloroform and distilling off the chloroform-water azeotrope which contains 2.5% water and boils a t 56.1" C. (6). Preliminary experiments with a distillation assembly and trap (similar to Hercules moisture trap, Scientific Glass Co. 5-2078) indicated that water could be removed and the monomethylamine hydrochloride precipitated.

The final design of the apparatus is shown in Figure 1; the large bulb makes it possible to run several successive determina-

loa 0

REfERENCE - OISTILLEO BENZENE INSTRUMENT-BEWMAN MM)EL* 22593 &REAGENT BLANK B I O L ~ p o ~ z o m l . c.oo.9 )rq/zoml.

Figure 2. Absorption of Cupric Dimethyldithiocarbamate

very simply by absorbing the amine in aqueous hydrochloric acid and subsequently removing the water by azeotropic distillation with chloroform; the monomethylamine hydrochloride is precipitated and the dimethylamine hydrochloride is quantita- tively recovered in the residual chloroform. Neither ammonia nor methanol interferes. The standard deviation of the determination for mixtures contain- ing 0.18 to 3.5070 dimethylamine in monomethyl- amine and trimethylamine is less than 0.05% abso- lute and the average error is within this limit.

tions without emptying the trap. If the flask, containing 50 ml. of chloroform, is heated by an efficient hot plate, the water from a 5 4 . aliquot of the sample can be removed in approximately 1.5 hours. The monomethylamine hydrochloride precipitates on the sides and bottom of the flask and the dimethylamine hydrochla- ride remains in the chloroform solution. The recovery is quanti- tative only if the last traces of water are removed, and for this reason the distillation must be continued for a t least 30 minutes after the first appearance of the monomethylamine hydrochloride precipitate. In standard practice, a 1-hour distillation follows appearance of the precipitate.

The methods adopted for the determination of dimethylamine in gaseous monomethylamine and trimethylamine apply equally to solutions of the amines, except that the use of a sampling tube is unnecessary. The technique used in sampling methylamines has been described ( 5 ) .

PROCEDURE

Standard Curve. A volume of 1.9 ml. of 40y0 dimethylamine solution is transferred to an Erlenmeyer flask containing 50 ml. of distilled water and 1 drop of methyl red indicator. The solu- tion is titrated with 0.5 N sulfuric acid to the first permanent pink color and is then diluted to 1 liter in a volumetric flask. From this solution, a working standard containing approxi- mately 7 micrograms of dimethylamine per milliliter is prepared by dilution.

Aliquot,s of 1 to 20 ml. of the dilute dimethylamine sulfat,e solution are transferred to 125-ml. glass-stoppered Erlenmeyer flasks and sufficient, water is added to bring the volume to 20 ml. Blanks containing only water are also set up. To each flask are added 2.00 ml. of ammoniacal copper solution and 20.00 ml. of the carbon disulfide-benzene solution. The tightly stoppered flasks are placed in the water bath, allowed to remain for 3 minutes, then removed and shaken violently for 30 seconds. To each flask are added 2.00 ml. of 30% acetic acid and the stop- pered flask is again shaken violently for 30 seconds. After stand- ing for 10 minutes, the benzene layers are decanted in turn into the spectrophotometer cell and the absorbancy, against benzene as a reference, is measured a t 440 mp on the Coleman instru- ment or 434 mp on the Beckman spectrophotometer. A cali- bration curve is prepared from the data obtained. The ab- sorbancy of the blank is usually negligible and constant.

Twenty-five milliliters of sulfuric acid (0.5 to 5 N ) and 1 drop of methyl red indicator are transferred to a Foust tube and the tube is weighed. The sample is run into the acid (6) to the yellow end point and the tube is reweighed. The excess base is back-titrated with a few drops of acid, and the solution is diluted so that it contains approximately 1 to 5 micrograms of dimethylamine per milliliter. Twenty-milliliter diquats of this solution are treated as described above for the preparation of the calibration curve and the amount of dimethylamine in the aliquot is obtained by reference to the curve. The concentration of dimethylamine in the sample is then calculated in the usual manner.

Monomethylamine Samples. The sample is run into 50.0 ml. of 2 N hydrochloric acid and the sample weight obtained a8 above. The solution is then diluted to volume in a 100-m1. volu- metric flask. A 5.00-ml. aliquot, of this solution is transferred to the Erlenmeyer flask of the distillation assembly and 50 ml. of chloroform are added, The apparatus is assembled and 10 ml. more of chloroform are placed in the trap, if it is empty. The solution is refluxed a t a rapid rate until a precipitate appears and then for an additional hour.

Analysis of Trimethylamine Samples.

1782 A N A L Y T I C A L CHEMISTRY

with acetic acid Dermits seuara- Table I . Results of Analyses of Synthetic Samples tion of the benzene and aqueou-

Weight of To. Average Average layers and a more complete PS- salliple , Coinposition of Samples, % sample i n of D i Average D i

S O . " Mono Tri D i Aliauot Detil. r o u n d Deviation Recovered traction Of the cupric dimethyl-

1

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27

. . . . . . . . . . . .

. . . 0.19 0 .19 0.20 0.58 0.58 0.59 1.43 1.44 1.45 1.45 4.07 9.36

32.81 96.43 96.92 98,48 98,49 98.68 98. 96 99.08 99.69 99.74

99.82 99.51 98,95 98.27 98.02 98.94 98 23 99.62 Y8,5t5 97,87 99.23 97.03 97 .70 98.,55 98.46 92.28 63.73 62.33

1.00

0.11

. . .

. . .

0 .18 0.49 1 .05 1.73 1 . 9 8 0.87 1.56 0 .18 0.87 1.55 0.18 1.54 0.86 0.0 0.09 3.65

26.91 4 .86 3.57 2.08 1.52 1.40 1 .31 1.04 0 92 0.31 0.26

9,s.; 10 .11 9 .94

10 .01 5.04 9.94

10.01 9.87 9.98

10,03 9 . 9 1

10.14 10.07 9 . 9 8 9.99 0.48 0.52 3.38 2 . 7 0 5 .26 7.94 8 .71 9 .24

10.71 6.58 7.84 9.14

2

4 I) 2 2 3 2 4 2 4 6 2 3

Coleman Nodel 11 spertrophotolueter used on samples 1 to 18, Beckinan

~~~- ~ ~ _ _ ~ _ _ ~

The flask is then removed from the appitratus, stoppci.ed, :ind allowed to cool to room temperature. The chloroform solution is decanted through glass wool into a dry 100-ml. volumetric flask and the Erlenmeyer flask, precipitate, :tiid funnel are washed several times with anhydrous chloroform. The filtrate and collected Lyashings are diluted to volumc, and a .i-ml. aliquot is transferred t o a 125-ml., glass-st>oppered Erlenmeyer flask containing 20 ml. of water. The chloroform in the aliquot is t,hen evaporated off on a steam bath or warm hot plnte so that no appreciable amount of water is lost. The remaining aqueous solution is then treated as previously described to develop the color and the diniethylaminr in the original sample is drtermined.

Table I lists the composition and analytical results obtained with aqueous solutions made up from pure monomethyl- amine and trimethylamine hydrochlorides. -4n average of 98.5% of the dimethylamine present was recovered froin synthetic mono- methylamine samples (Nos. 16 to 27) and 101.0% from synthetic trimethylamine samples (Nos. 1 to 15). The standard deviation of the recovery of dimethylamine in synthetic monomethylamine samples n a s l.iCo, while that for the trimethylamine samples was 1.4%, equivalent to approximately =tO.O2C/, in a sample containing 1 % dimethylamine.

The dimethylamine content of eight production samples of monomethylamine and trimethylamine was determined and the t,otal dimethylamine redetermined after addition of the appropri- ate dimethylaniine salt solution. The total dimethylamine present ranged from 0.24 to 4.0y0 and the mean of the recovery of the total dimethylamine present was 98.7%. The standard deviation of a series of app1;osimately 125 determinations by sir :inal>-sts on fifteen production samples \vas &0.05% absolute.

Results.

DISCUSSION

The chemistry of the cupric dimethyldithiocarbamate pro- cedure has been discussed by Dowden, who esplained the function of the ammonia as that of an emulsifying reagent for the benzene anti aqueous solutions. It has been pointed out ( 7 ) , however, that the excess ammonia functions also to drive the carbamate reaction to completion by displacing the amine from the di- inethylammonium dimethyldithiocarbamate salt : (CH,)?NH&3CS(CH,), + SHd+ F;i

I1

s

S The released amine then reacts with the carbon disulfide present

Subsequently, the neutralization of the ammonia as ciescribed.

% "0 % dithiocarbamate. The use of 0.19 1 0 . 0 1 105.2 mineral acid is precluded in

order to avoid the decomposi- 0.50 +0.01 100.8 1.03 1 0 . 0 0 98.4 1.74 +0.01 100.3 tion of the thiocarbamate. 2 . 0 2 1 0 . 0 2 101.9 0.88 1 0 . 0 1 100.0 The negligible interference of

monomethylamine when present 1.57 1 0 . 0 2 100.5 0.19 zto.01 166.3

in Ion- concentration is a result 0.87 1 0 . 0 1 99.7 1.55 zto.00 100.2 0.17 1 0 . 0 0 97 .7 t ~ f t i v o factors: the relative in-

soluhility of the cupric niono- 1.56 *0.02 100.8 0.86 1 0 . 0 2 100.2 0 .01 1 0 . 0 1 meth!.ldithiocarbani:~te in ben- 0.09 = t O . O O 103:4 3 . 8 1 0 . 1 103.4 zene and the fact that the peak

of the absorption spectrum of 26.5 +0.9 98 .7 5 , 0 1 0 . 0 103.0

this salt is in the rtJgion of 360 3.64 ztO.06 98.9 2.05 + a . 02 98 .7 1.52 =0.01 99.6 nip while that of the dimethyl-

amine derivative is a t 434 mp. 1. 3s r 0 . 0 2 99 .6 1 . 3 1 zto.01 100 2 1 .02 1 0 . 03 97.9 In general, for maxiniuni 0.90 +0.02 97 .7 0.32 1 0 . 0 1 103.3 precision, the size of the saniple

should he adjusted so that 20 to 0.25 *a 01 93 8

120 micrograms of dimethyl- amine are taken for the analysis. .-iliquots containing 6 to 7.5 my.

of total amines ai'(' taken \\-lien determining amounts of dimethyl- amine betiwen 0.2 :rnd 2.070.

It is possilile to exteiid the procedure to mixtures of amines cont:hing as murh as of dimethylamine if the sample is properly diluted. The results xith such samples tend to be low by 1 to 2% absolute and precision of the same order of magnitude is obtained. The method has been found useful for samples of this type when only approximate analyses are required.

Eithrr the hydrochloride or sulfate salt may be usrd for the determination of dimethylamine in the absence of considerable monomethylamine. However, the amine sulfates cannot be used in the separation of monomethylamine because of the relative insolubility of the dimethylamine sulfate in chloroforni.

The determination of dimethylamine in ti~iniethylamine re- quires approximately 1 hour of elapsed time while the deter- mination in monomethylamine requires approximately 3 hours, much of which is consunied by the distillation step. For routine work, the usr of a photoelectric. colorimeter with appropriate filter has been found satisfactory.

Model I)U on samples 1 9 to 2 7 .

ACKNOWLEDGMENT

The authors wish to express their appreciation to I\-illiam , Scanlon, David Lentz, Eleanor Fuller, Jack Cline, Stanley Haas,

and Alfred Livingood for some of the analyses reported here, and to the many members of the Rohm and Haas organization who have aided with advice and suggestions.

LITERATURE CITED

(1) Uertheaiime. .J.. Conipf. .i.md.. 150, 1251 (1910). (2) Dowdcn, H. C. , Biochrm. J . . 32, 455-9 (193s). (3) Duke, F. R., IND. ENG. CHEM., .IXAL. ED.. 17, 196 (1945). (4) English, F. L., ASAI.. CHEM.. 23, 344-6 (1951). (5) Gore, J. L., Baum, Harry, and Stanley, E. L., Ihid. , 23, T21

119511. (6) H O i i e y : L. H., Ib id . , 19, 509 (1947). (7) Katcher, E., and Voroshilora, A I . , Anilinokrascohnaya P r o m , 4.

(8) Smales. -1. A, and Wilson, H. N., J . SOC. Chem. I n d . , 67, 210-1.1 39-41 (1934).

(1948). (9) Stanley, E. L., and Savacool. R. V., hZeeting-in-~~llixiiatuie.

Philadelphia Section, -%XERICAX CHEXICAL SOCIETY, Jan. 20. 1949.

(10) Weber, F. C., and Wilson, J. B., J . Biol. Ckem., 35, 385-410 (1918).

RECEIVED April 12, 1951. Presented before Section 2, .Inalytical Chemistry, a t the X I I t h International Congress of Pure and Applied Chemistry. S e w York, PI'. Y., September 10 t o 13, 1931.