140
T H E J0URAV.IL O F Il17DI;STRIAL A,VD E~VGINEERI~\TGC H E M I S T R Y
t o dissolve in. or thoroughly absorb, chloroform. A small Florence flask ( 7 5 cc.) is used, which may be about one-half full of t h e solvent. Nitrous oxide vapors, evolved from dilute nitric acid (sp. gr. 1.3) a n d arsenic trioxide: are t h e n passed through t h e cooled chloroform until t h e deep green color becomes permanent for about I j min., a n d t h e whole allowed t o s t a n d over night for completion of t h e action. The chloroform i.5 t h e n decanted through a dry Gooch crucible a n d asbestos m a t t e (the former rests i n a n ordinary 60' filter funnel) into t h e combustion flask, from which t h e chloroform is t h e n evaporated b y means of a boiling water b a t h a n d a d r y air current.' hIeanwhile t h e residue i n t h e Florence flask has been similarly dried. T h e separation of fillers a n d nitrosite is now brought ahout in t h e following way: Small portions ( j cc.) of calcium chloride-dried ethyl acetate are added t o t h e residue i n t h e Florence flask, t h e l a t t e r warmed, a n d t h e liquid decanted through t h e Gooch crucible into t h e combustion flask! repeatedly. until t h e filtrate runs through entirely colorless. ,%fter evaporation of t h e acetate (recovery of t h e solvent as well), t h e residue is carefully freed from solvent b y warming t h e containing flask in a boiling water b a t h for 'about I j min., after which I j cc. of water, containing I drop conc. HC1, is added, a n d quickly evaporated by t h e use of a boiling calcium chloride b a t h a n d brisk current of dry air. T h e heating is continued a t least ' / ? hr. after t h e residue is again apparently d r y . T H E c o m r s T I o x A P P A R A T U S consists of a 2 0 0 cc. round-bottom distilling flask, which is provided with a dropping funnel (100 cc.) through a one-hole rubber stopper, a n d a series of U-tubes containing in order, ( I ) conc. H2SO4-K2Cr207, renewed every I or 2 combustions, ( 2 ) water containing a drop of t h e preceding, (3) granular zinc, (4) calcium chloride, (j) soda-lime (weighed)! (6) soda-lime a n d calcium chloride (weighed). T H E conmusTIoP-The weighed soda-lime tubes i n position, a n d t h e combustion flask cooled b y water, a Volume ( 2 0 cc.) of cooled concentrated sulfuric acid is r u n rapidly i n t o t h e flask onto t h e nitrosite; t h e n t h e cooled oxidizing solution of I O g. pulverized K2Cr207i n 7 j cc. conc. HzS04, i n a very slow stream. T h e flask may now be gently warmed b y a sand b a t h t o obtain a moderately rapid evolution of gas.? This is done as long as gas continues t o be evolved (about a n hour), when a carbon dioxide-free current of air, t h e heating being maintained, is passed via t h e dropping funnel through t h e apparatus for at least '/* hr. t o sweep all carbon dioxide into t h e soda-lime tubes.
W t . COS
X
136 440
X
zoo
gives percentage
C10H16in t h e sample. We hope? in conclusion, t h a t further s t u d y a n d im1 Mr. J. H . Tuttle of the Bureau of Standards has found t h a t the chloroform-soluble residue thus recovered may be very appreciable, and i t is t o his suggestion t h a t this modification is dlie. ' T h a t carbon monoxide is formed during the combustion can be shown by allowing t h e gases which have passed the absorption train t o come in contact with heated copper oxide a n a then barium hydroxide solution. A precipitate ensues, but the amount is not appreciable for the results of the analysis.
5'01. 9 , N O . 2
provements of this method will eventually give a reliable a n d not too difficult procedure for t h e direct determination of rubber, not only in good quality compounds b u t also i n factis and other inferior substitute-containing rubbers. CASE:
APPLIED S C I E S C B CLEVELAND, OIIIO
S C H O O L OF
DETERMINATION OF MINERAL FILLERS IN RUBBER ANILINE METHOD By OTTO H. KLBIN, J
O H ~ H.
LINK AND FRANKGOTTSCH
Received October 23, 1916
Although t h e use of aniline as a solvent for vulcanized rubber is not new, there is very little information t o be found concerning such use in t h e literature. We have. therefore, thought t h a t a n account of t h e method as far as i t has been worked o u t . t o gether with some analyses of samples of known composition, mould be of interest. This report should be considered as a preliminary one, as t h e supply of rubber mixings a t h a n d for our experiments was limited a n d other rubber fillers t h a n those used are yet t o be experimented with. I n making t h e determination it is essential t h a t t h e sample be finely powdered ( 2 0 mesh). A I-gram s a m ple is extracted with acetone for 4 hours, dried a t a low temperature, a n d t h e n transferred t o a weighecl I O O cc. centrifuge t u b e . T h e residue is covered with jO cc. of pure aniline, j cc. of nitrobenzene added, t h e mixture stirred, covered, a n d heated a t 160' C. with occasional stirring until solution is complete. I t is our practice t o heat t h e samples over night in a Freas oven. I n most cases solution is complete by t h e next d a y . Sometimes t h e sample dissolves in 3 t o 4 hours. If t h e rubber is not yet i n solution, this can be seen b y stirring with a glass rod. When solution is complete, there is nothing t o be seen b u t fine pigment, free from rubbery appearance.' T h e t u b e is allowed t o cool sufficiently, filled u p with ether a n d well stirred. I t is t h e n centrifuged for I j minutes a t Ijoo r. p. m. T h e supernatant liquid is decanted, about 2 5 cc. of ether added a n d t h e pigment stirred u p completely. It is centrifuged again a n d t h e decantate added t o t h e first. Four such washings with ether are necessary. T h e tube is dried a t 100' C., cooled a n d weighed. T h e united decantates are evaporated a n d t h e n ignited in a weighed porcelain or silica dish; t h e weight of fillers found is added t o t h a t i n t h e tube. T h e percentage of fillers plus t h a t of t o t a l acetone extract is subtracted from I O O per cent, a n d t h e difference recorded as rubber gum. Aniline differs from other solvents in t h a t rubber dissolved i n i t forms a t h i n solution which permits t h e mineral fillers t o separate readily. The small a m o u n t of nitrobenzene used, causes a more rapid solution. I t was found t h a t semicured compounds dissolve more slowly t h a n thoroughly cured soft stocks or very h a r d ones. With undercured compounds a s o f t pasty mass is formed, which 1 The chemist who makes the analysis for the first time may be uncertain of himself a t this point, b u t after one or two determinations have been made he will a t once recognize any undissolved rubber.
T H E JOI-RLV.-1L O F I.YDCSTRI'1L
F e b . 1917
d-VD EAVGIJEERI-VG C H E M I S T R Y
T A B L E I-RESLLTS O h SAMPLI 5 O r I ( h O n Y CO\lPOsITIO'i ."XILINE h r G T H O D FOR FILLERS 0 No 1 0 No 2 H I J UNO 1 L No 1 G X o 1 (Percentages) COMPOSITION OF SAMPLES 40.6 37.0 30.0 40.0 40 1 40.0 40.3 40.3 Pure Rubber (Fine). . . . . . 3.0 3.0 2.c 4.0 3.0 3.0 2.0 2.0 Sulfur.. . . . . . . . . . . . . . . . . 56.4 30.0 30.0 14.0 18.9 ... 18.9 1s.9 Zinc Oxide.. . . . . . . . . . . . . . . . 15.0 18.9 . . . 1 8 . 9 18.9 Xvhite Lead ( D u t c h ) . . . . . . ... ... 9.9 ... 9.9 9.9 Light Magnesia CarbonaLe ... ... 2.0 2.0 Hydrated- Lime ... 15.0 8 0 8.0 Litharge, . . . . . . . . . . . . . . . . . . . .. , . . . . . . . Xvhiting . . . . . . . . . . . . . . . . . ... ... ... 20.0 ... ... ... ... Lithopone. . . . . . . . . . . . . . . . . . . . . 1 5 . 0 . . . . . . . . . Vermilion . . . . . . . . . . . . . . . ... ... ... ... ,.. Carbon B l a c k . , . . . . . . . . . . ... 1h:'O ... ... ... ... Golden -1ntirnony. . . . . . . . ... ... 5.0 ... ... ... Maguesium Oxide. . . . . . . . , . . . . . 1 7 . 0 . .. . . . . . . Aluminum Flake.. . . . . . . . ... ... ... 33.0 ... ... Sublimed White L e a d . . . ... ,.. ... ... ... ... Asbestos. . . . . . . . . . . . . . . . Plumbago, . . . . . . . . . . . . . . I C u r e . . . . . . . . . . . . . . . . . . . ZO'X'40 9 0 ' X 4 0 100 x '%O0 F. 100 X ' 2 . 5 0 O F. 100 X' 2'50' F. 8 0 ' 2 30 .4KAI,STI(:BL RESVLTS(PERCENTAGES) B Y AKILIKE METHOD 5 s . 60 57.56 60.03 55.00 67.03 59.36 58.72 58.76 Fillers F o u n d . . 67.79 54.x ... 57.40 ... 58.40 I58.71 59.43 1.29 1.31 0.99 1.19 0.74 1.09 1.23 1.03 Organic Acetone E s t r a c t 2.00 4.50 0.88 1.82 0.9; 2.24 0.42 0.20 Free S u l f u r . . . . . . . . . . . . . . 39 34 39.53 39,33 36.86 39.44 29.60 39.75 39.17 Rubber.. . . . . . . . . . . . . . . . 0.44 8.21 0.00 0.32 9.32 0.47 0.1s Fillers in D i s h . . . . . . . . 6 9.5 ... 0.09 5.51 ... 0.82 0.36 , J , Caucho Rubber
SamDle T u m b e r
is yery slow t o dissolve, while this does not occur if the material is properly vulcanized. .We found t h a t in a few cases a n additional digestion with half t h e q u a n t i t y of solvent for j hours reduced t h e amount of mineral fillers about 0 .,j per cent. In specification work it is advisable t o make this second digestion after t h e ether has been expelled from the t u b e b y heating. In Table I , Samples 0 No. I a n d 0 KO. z are t h e same, except t h a t 0 S o . z was purposely overcured. Sample H was prepared using t h e same recipe as for Samples 0 Nos. I and 2 , b u t b y another manufacturer. Samples H, I and J were unintentionally undercured. Sample C is a hard valve. Sample G No. 14 contains Caucho rubber. Analysis of t h e fillers showed t h a t t h e rubber as found b y difference did not include all the sulfur of vulcanization. I t will be noted t h a t t h e s u m of t h e percentages of rubber found a n d of t h e organic acetone extract is slightly greater t h a n t h e percentage of rubber used in t h e recipe. T h e fillers during vulcanization and afterwards in the course of analysis have combined with sulfur t o form new compounds. If this combination of fillers and sulfur is a substitution of sulfur for some other acid radical, the resultant product would usually weigh less t h a n t h e s u m of t h e ingredients entering t h e reaction and t h e rubber found b y difference would be slightly greater thereby. We expect t o continue these experiments when other samples are available, and a final report will be made on the subject when we shall have all t h e d a t a a t hand. BOilRD O F E S T I M A T E A N D APPORTIONMENT CENTRALTESTING LABORATORY 125-177 n ' O R T H ST., XEW YORK CITY
THE FREE CARBON OF WOOD-TAR PITCHES By H. K. BENSONAXD L. I,. DAVIS Received November 27, 1916
In t h e examination of wood tars, it x-as found t h a t t h e so-called "free-carbon" of t h e residuums was esceptionally high as determined b y t h e methods generally employed for this purpose.' I t was accordingly 1 Office
of Public Roads, U
D e p t . 4gric.. Brcil. 314, I). 25.
141 C
GiXo. 14
24.44
37.0(a)
...
ii:il 4.44 6.67 6.67
... ...
3.0 30.0
...
.. ... ... ,
, . .
...
i4.11
60.44
0.80
5.04 1.48 33.04 3.60
...
0.30 24.79 I .4.3
. .
... ...
considered worth while t o ascertain whether the carbonaceous residue from carbon disulfide extraction really consisted of carbon or of probable hydrocarbons t h a t are insoluble in carbon disulfide. Previous work had already shown a marked variation in t h e solubility of bitumens in t h e usual petroleum solvents. wood-tar pitch being almost completely insoluble in petroleum distillates or turpentine. and only slightly soluble in benzol. T h e relative solubility of bitumens was therefore determined in carbon disulfide and acetone b y t h e usual method. T h e resulting residue insoluble jn a given solvent was in each case again extracted with t h e other solvent. T h e wood tars were obtained from the experimental wood distillation plant a t the University of Washington, from n commercial plant in Oregon and from a hard wood distillation plant i n Michigan. Commercial coal-tar pitches were t a k e n from a local Barrett plant, t h e petroleum asphalt from a city paving plant and t h e Trinidad asphalt from a laboratory sample. T h e results are given in Table I . TABLE I-RESPECTIVE SOLUBILITIES OF BITUMENS I S ACETONE AND C.4RBON DISULFIDE
IPI'SOLUBLE I K CSI
SAMPLE Douglas fir pitch . . . . Douglasfirpitch. . . . Douglas fir pitch.. . . Douglas fir Ditch.. . . H a d wood 'pitch., , , H a r d wood p i t c h . . . . Coal-tar pitch.. Coal-tar pitch.. Coal-tar pitch.. Coal-tar pitch.. Petroleumasphalt . . . Trinidadasphalt.. , ,
..... ..... ..... .....
Per cent 67.7 62.5 93.1 60.2 18.7 59.9 27.4 22.7 18.4 17.4 4.1 42.6
Residue insoluble in acetone 59.7c/, 30.1 35.3 22.0 3.1 18.0 27.4 22.6 18.0 17.1 4.0 42.1
INSOLUBLE IN
ACETONE XELTResidue ING ASH insoluble POINT Per in CS2 F. cent 57.853 200 2.9 31.1 185 1.0 34.4 150 0.8 21.3 130 0 I 2.7 0.1 17.4 0.';' 27.1 l., 22.3 0 6 18.5 0.1 16.9 0.0 3.9 95 0.0 41.8 150 31.2
Per cent 57.7 31.6 34.6 21.5 -2.9 17.5 57.5 37.1 35.3 33.0 27.1 69.0
CONCLUSIONS
I-The free carbon of wood-tar pitches cannot be determined b y carbon disulfide. 11-Acetone is suggested as a solvent in this determination for wood-tar pitches. 111-Coal-tar pitches may be classed with t h e native and t h e manufactured asphalts for t h e determination of free carbon. L.4BOR.4TORY O F I N D U S T R I A L CHEMISTRY cSIVERSITS O F \\'ASHINCTOS SEATTLE
