T H E J O l ’ R S d L O F I Y D L - S T R I . 4 L A.VD E S G I S E E R I S G C H E M I S T R Y
J u n e , 1913
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sulfur. This will be brought o u t in t h e discussion JV hi ch f 011ow s . I t will be seen from t h e equations given above t h a t t h e compounds formed b y t h e reaction between calcium hydroxide a n d sulfur, under ordinary commercial conditions of manufacture, are calcium tetrasulfide, pentasulfide, thiosulfate. a n d sulfite. All of these compounds are readily soluble in water with t h e exception of t h e sulfite. which is comparatively insoluble. This being t r u e , t h e chemical analysis of t h e limesulfur solution shows t h e a m o u n t s of lime (slaked with water t o form hydroxide) a n d sulfur t h a t have reacted in t h e formation of t h e same except t h e a m o u n t s of these substances necessary t o form t h e insoluble sulfite produced. F r o m t h e knowledge of t h e chemical reactions t h a t occur. however, i t is not a difficult m a t t e r t o estimate. from t h e chemical analysis of t h e solution, t h e q u a n t i t y of sulfite which has been formed. Equation ( I ) shows t h a t when calcium hydroxide a n d sulfur combine. one-third of t h e celcium is combined as thiosulfate a n d two-thirds as polysulfide. Since there is no decomposition of t h e polysulfide, t h e q u a n titative estimation of t h e calcium combined in this form gives a means for determining t h e a m o u n t of thiosulfate which has been formed. T h e difference between this tote1 estimated e m o u n t of thiosulfate a n d t h e a m o u n t actually present in t h e solution. is t h e q u a n t i t y t h a t has decomposed; a n d from this d a t a t h e a m o u n t of sulfite can be easily calculated. T h e initial ratio of lime t o sulfur is also easily determined when one knows not only t h e a m o u n t s of calcium a n d sulfur present in a given lime-sulfur solution, b u t also t h e insoluble sulfite produced in t h e preparation of t h e same. T h e analytical methods for determining t h e a m o u n t s of calcium combined a s polysulfide as well as t h e a m o u n t s of other constituents of lime-sulfur, have been very thoroughly worked o u t ’ a n d i t is unnecessary t o discuss t h e m in this paper. T h e actual application of t h e discussion given above is brought o u t in Table I . T h e chemical compositions of several samples of commercial lime-sulfur solution are given; also t h e estimated a m o u n t s of insoluble calcium sulfite formed a n d t h e calculated ratios of lime TABLEI-CHEMICAL
COMPOSITIOS LIME ( C a O )
7
-----
Combined a s
S o . Sr G R . 1,2585 1.3335 1 2825 1 ,2560 1,2820 1.3110
( a ) Not
.
Estimated Poly-Thio- as insol. sulfide sulfate sulfite 9 464 1 , 8 2 0 4 . 0 6 0 13.943 0.672 5.152 11.357 1 . 1 2 0 4 558 1 0 . 2 4 8 1.008 4 , 1 1 6 11.424 0,840 4 . Xi2 11.802 1 . 1 9 8 4 . 7 0 3 1 0 . 8 3 4 I . 286 4 . 1 3 1 determined
OF
LIME-SVLFUR SOLUTION S U L F U R( S )
dilute solutions prepared under commercial conditions. I t is evident, however. from t h e work of Thatcher’ a n d V a n Slyke2 t h a t t h e ratio in this case would be somewhat greater t h a n I : a ; in some cases it would be perhaps I : 2 . 2 j. The theoretical basis given here mill not exactly apply, of course, t o t h e preparation bf small a m o u n t s of solution, s a y I j o gallons or less. where t h e oxidation of t h e polysulfides occurs t o a considerable extent through contact with t h e air. Acknowledgment is due t o N r . R . H . Robinson mho made several of t h e chemical analyses reported above. CHEMIC4L
.4GRICULTUR4L EKPERINEXT STATIOX CORVALLIS. OREGON
L4BOR4TORY.
THE DETERMINATION OF CAMPHOR IN TABLETS AND PILL s ny EDWINDOWZARD Received M a r c h 9, 1914
In so far as t h e writer has been able t o learn, the methods used elsewhere for t h e determination of camphor in tablets a n d pills have not pro\*ed satisfactory. For this reason a description of a method is given which has been in use for over five years with satisfactory results: Camphor m a y be rapidly a n d completely removed from tablets a n d pills b y distillation in a current of s t e a m . T h e watery distillate contains both dissolved a n d undissolved camphor, which can be extracted with benzol. By determining t h e optical rotation of t h e benzol solution. t h e a m o u n t of camphor present in t h e tablets or pills can be readily calculated. A special a p p a r a t u s is required for t h e distillation, because a n ordinary condenser cannot be used a s t h e camphor blocks up t h e tube. After a number of trials t h e arrangement shown in t h e figure proved satisfactory. T h e a p p a r a t u s consists of a flask. -1. for generating steam, a second flask, B , for t h e steam distillation. a n d a receiver, C (a retort with t h e t u b e bent as s h o w n ) , for t h e distillate. T h e retort is kept cool b y t w o streams of water ( D a n d E ) . D impinges on t h e wide p a r t of t h e neck, a n d E on t h e extreme e n d of t h e t u b e . which is closed with a rubber stopper fitted with a glass t u b e open a t both e n d s , t h u s every p a r t of t h e retort is kept covered with a film of water, ensuring a complete condensation. T h e large funnel F conveys t h e water t o a sink b y means of a rubber tube. T h e funnel should be kept a b o u t half filled with water, t h e flow of water from t h e funnel being regulated b y pinchcock G. P R O C E D U R E F O R A DETERMISATIOS-.I number of t a b lets or pills containing about z 1 2 t o 3 grams of camphor are placed in t h e flask B . T h e tablets are just covered with water a n d t h e a p p a r a t u s connected. Sufficient water t o cover t h e bottom of t h e t u b e H is placed in t h e retort. T h e water in -4 is now boiled, with I closed. t h e steam passing into B through t h e t u b e , which a1n:ost
_ A -
Combined as Polysulfide 2 6 ,313
3i.498
30.780 2 7 . 926 31.283 31.930 28 980
Esti-
mated insol. sulfite 2 320 2 944 2 604 1 . 1 5 2 2 354 0.960 2 i84 1 . 3 7 0 2 688 1 . 4 7 0 2 360
Thiosulfate 2.080 0.768 1.280
as
RATIO CaO : S REOUIRED 1 : 2.00 1 : 2.08 1 : 2.03 1 : 2.04 1 : 2.04 1 : 2.04
1 : 2.01
t o sulfur. T h e results relating t o chemical composition are expressed as grams per I O O cc. of solution T h e d a t a given s h o r t h a t t h e proportion of lime ( C a O ) t o sulfur which react in t h e preparation of t h e more concentrated commercial lime sulfur solutions is b u t a mere trifle greater t h a n I : a . Unfortunately t h e a u t h o r has not h a d opportunity t o examine more 1 J o u r . A m e r . Chem. Soc., 27 (1905). 244; THISJ O U R N A L , 2 (1910), 271; Alich. Agr. Exp. Sta., Tech. Bull. No. 6.
489
1
Jour A m e r Chem S O L ,30 (19081, 63
2 LOC
c1t
.lSD ESGISEERISG CHEMISTRY
'
touches t h e bottom of t h e flask, carries over the camphor from the disintegrated tablets. The distillation is continued until the distillate measures about joo cc.
1-01. 6 , KO.6
If t h e pills or tablets do not disintegrate readily, they should be coarsely ground in a mortar, before distilling. The writer has determined t h e rotation of a number of samples of camphor. All esamined had practically the same rotation. The following figures give the camphor equivalent in j o cc. of benzol solution for each o o I ' of rotation: Rotation taken in 100 mm. tube a t 25' C. Grams camphor Total dissolved in volume benzol Cc. Rotation Camphor 6 50 00 1' =0.01940? 3 50 00 1' = O . 019745 1,s 50 0 0 1' =0.01969? Average 0' 1' =0.019613 gram of camphor in 50 cc. or 0.009806 gram camphor in 25 cc. for each O o 1' of rotation.
To test t h e apparatus, 2 grams of camphor were distilled and the distillate extracted with 2 j cc. of benzol, as described. The following figures were obtained : Rotation in 100 mrn. tube a t 25O C. = 3' 5' or 185'. As t h e above solution consists of 2 grams of camphor and 25 cc. of benzol, not 2 grams made up t o 25 cc., a correction is necessary and is determined as follows: 185' X 0.009806 = 1.8144 C From t h e figures previously obtained, we know t h a t the above rotation indicates t h e presence of 1.8144 grams of camphor in 25 cc. of t h e solution. It is now necessary t o calculate how much benzol we have in 25 cc. of this solution. As t h e specific gravity of camphor a t 25' C . is about 0.99, 1.8144 grams of camphor displace 1.8324 cc.
'fir
= 1.8324
Therefore, we have 23.1676 cc. of benzol in 25 cc. of the solution. 25.0000 cc. 1 ,8324 cc. 23,1676 cc. S o w if 23.1676 cc. of benzol have 1.8144 grams of camphor, 2 5 cc. will have 1.957 grams. 1.8144 -. X 25 = 23.1676or. 97.85 per cent of the amount taken. ~~
I
4
The pinchcock I is now opened a n d the flame removed from A . The water is allowed t o run over t h e retort for j minutes longer t o thoroughly cool t h e distillate. The retort is now disconnected, leaving the t u b e H with t h e pinchcock J attached a n d screwed tight; 2 j CC. of benzol measured a t 2 j O C. are allowed t o flow into t h e retort through t h e neck, after removing t h e rubber stopper fitted with t h e glass tube opened a t both ends. The retort is securely closed with a rubber stopper and the contents vigorously agitated for several minutes. The position of the retort should be frequently changed t o allow the benzol t o reach every part, thus ensuring t h a t all t h e camphor is dissolved in t h e benzol. The mixture is transferred t o a separator, t h e water drawn off, and t h e benzol solution of camphor filtered through ' a small plug of cotton wool into a I O O mm. tube, t h e rotation being taken a t 2 j" C.
I
Several determinations were made with varying amounts of camphor, with very close results. I t will be seen t h a t a slight correction is necessary for loss. As each apparatus a n d t h e manipulation of different chemists will vary somewhat, several determinations, using known weights of camphor, should be made and the factor for t h e apparatus calculated. The factor for t h e apparatus used by t h e writer is 0.01001 gram of camphor for each o o I ' of rotation in I O O mm. tube a t z j o C. The average amount of camphor in the tablet or pills is obtained by dividing the number taken into t h e weight of camphor found. Using the above ,method, a determination may be completed within two hours. ANALYTICAL DEPARTMENT, PARKE,DAVIS & Co. DETROIT, MICHICAX
LABORATORY AND PLANT THE STATUS AND TENDENCY OF THE GAS INDUSTRY' B y WALTERR. ADDICKS
T h e artificial gas business was never in so advantage1 Presented a t the meeting of t h e N. Y. Section of the Society of Chemical Industry, The Chemists Club, March 27, 1914.
I
ous a position strategically as at this writing, yet two influences are felt adverse t o progress: t h e first is an obsolete candle power standard; t h e second, which is not confined t o t h e gas industry, a tendency t o deny t o proprietorship a percentage return on investments commensurate with t h e character of t h e service and
