Aug., 1914
T H E J O U R N A L OF' I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
A METHOD FOR THE ESTIMATION OF PODOPHYLLUM RESIN By W. M. JENKINS Received April 24, 1914
It seems t o be a generally acknowledged fact t h a t t h e therapeutic activity of Podophyllum is due t o t h e resin which i t contains. While this resin is recognized in t h e United States Pharmacopoeia, a n d its properties and solubilities are well described, i t must be remembered t h a t t h e resin is not a simple substance, b u t a mixture of substances, t h e most important of which is a crystalline body called Podophyllotoxin. From a therapeutic standpoint, however, Podophyllum Resin, U. S. P., is a well known substance and t h e dose is well defined. It would seem therefore t h a t a n y a t t e m p t s a t assaying or standardizing t h e drug should be in terms of Podophyllum Resin, U. S. P. It was with this idea in view t h a t t h e work described in this paper was undertaken. All previous methods for t h e determination of Podophyllum Resin have been based on t h e idea t h a t t h e resin is insoluble in water, and t h a t by pouring a n alcoholic solution of t h e resin into a large volume of acidulated water t h e resin1 would be completely precipitated and could be collected a n d weighed. Through long experience with this precipitation method, however, it has been found t h a t t h e results are very unreliable a n d greatly affected b y t h e conditions of t h e method, v i z . , t h e volume and temperature of t h e acidulated water, t h e amount of alcohol used and t h e amount of sample taken. The only way t o get results which were a t all concordant was t o adhere strictly to t h e same amounts of alcohol, water, acid and sample; the results were t h u s purely arbitrary. T h e reason for these variable results was later found to be t h e fact t h a t Podophyllum Resin is slightly soluble in water and t h a t this solubility is increased b y small percentages of alcohol, and hence t h e recovery of the full amount of resin b y t h e precipitation method is impossible. Thus it was found t h a t b y dissolving 0.4 gram of U. S. P . Podophyllum Resin in I O cc. of alcohol and precipitating t h e resin in 600 cc. of water acidulated with I O cc. of hydrochloric acid, only 7 5 per cent of t h e resin. was recovered. Podophyllum Resin is only partly soluble in chloroform b u t is readily soluble in a mixture of I part of alcohol and 2 parts of chloroform. Hence i t was thought t h a t a mixture of alcohol and chloroform might be used for extracting t h e resin quantitatively from an alcohol solution which had been diluted with water. When equal volumes of alcohol, chloroform and water are mixed, this mixture separates, on standing, into two layers. The upper portion consisting approximately of one part of alcohol and two parts of water, and t h e lower layer of one p a r t of alcohol and two parts of chloroform. B y keeping t h e proportions of alcohol, chloroform and water constant, it was found t h a t over 99 per cent of resin was recovered b y three extractions with the alcohol chloroform mixture when working with U. S. P. Podophyllum Resin. 1
J . Chem. Sac. ( T r a n s . ) , 1898, p. 209.
671
When this method was applied t o t h e fluidextract, however, and t h e resulting resin compared with t h e U. S. P. Podophyllum Resin, i t was found t o be darker, more hygroscopic, less soluble in alcohol and more soluble in water. Thus it was necessary t o modify t h e method in some way in order t o obtain a resin identical with t h e official resin. This was accomplished b y washing t h e alcohol chloroform extract with acidulated water. T h e resin obtained b y this modification was found t o conform t o t h e United States Pharmacopoeia requirements for Podophyllum Resin, viz.: Soluble in alcohol in all proportions. 86.4 per cent soluble in ether. 69.1 per cent soluble in chloroform. 21.3 per cent soluble in boiling water. 0.1 per cent ash.
By this procedure from 0.4 gram Podophyllum Resin U. S. P. dissolved in alcohol, 0.394 gram was recovered, corresponding t o 98.4 per cent. Accordingly t h e following method for estimating t h e amount of Podophyllum Resin in Fluidextract Podophyllum is suggested. Measure j cc. of Fluidextract Podophyllum into a separatory funnel, add j cc. of alcohol, I O cc. of chloroform and I O cc. of acidulated water containing 0.6 per cent hydrochloric acid ( 2 cc. HC1 in I O O cc. water). Shake and allow t h e mixture t o separate. Draw off t h e lower layer into another separatory funnel; repeat th.e extraction twice, using I j cc. of a mixture of one part of alcohol and two parts of chloroform, each time, and add these extractions t o t h e first. Shake t h e combined extractions with I O cc. of t h e acidulated water and allow t h e mixture t o separate. Draw off t h e lower layer into a tared flask, and repeat t h e extraction twice, using I j cc. of t h e alcohol chloroform mixture each time. Evaporate t h e combined extractions and dry t h e residue t o constant weight a t IOOO
c.
For comparison a number of fluidextracts were assayed b y this method, and by t h e usual precipitation method with the following results: RESININ FLUIDEXTRACTS Precipitation method Shake-out method G . in 10 cc. Per cent G. in 5 cc. Per cent
1,,..... . . , . , , , , , , 0,424 2 . . . . . . . . . . . . . . . . . 0.420
3 . . . . . . . . . . . . . . . . .0 . 4 2 0 4 , . . . ., , . . , . , . , ,
,,
0.456
4.2 4.2 4.2 4.5
0.3480 0.3130 0.2895 0.3430
6.9 6.2
5.7 6.8
I n assaying t h e drug, I O grams in a No. 60 powder are placed in an Erlenmeyer flask, and 2 j cc. of alcohol are added. The flask is then fitted with a stopper through which is inserted a glass tube about two feet long for a condenser and left on a sand,bath a t 80° C. for three hours. The contents of t h e flask are then transferred t o a small percolator and washed with alcohol until about j o cc. of percolate are obtained. When cooled t o room temperature, t h e solution is made u p to exactly jo cc. Of this solution, I O cc., representing 2 grams of t h e drug, are used for assay, which is carried out in exactly the same way as described for t h e fluidextract, with t h e exception of the addition of the j cc. of alcohol, which is omitted. It was found t h a t it required a t least 48 hours macer-
.
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y ation with cold alcohol t o exhaust the drug, and hence the hot maceration is advisable. @Six different samples of Podophyllum were assayed by this method, and from t h e same samples fluidextracts were made according t o the directions in t h e United States Pharmacopoeia, and were also assayed. The results are given below: Grams resin in 100 grams drug 1 .......................... 5.03 5.24 2 . . ........................ 3 .......................... 4.65 4 .......................... 4.92 5 .......................... 4.73 6.82 6 ..........................
Grams resin in 100 cc. fluidextract 4.96 5.16 4.66 4.89 4.83 6.71
These results show t h a t t h e method gives very concordant results on t h e assay of the drug and fluidex-
I
Vol. 6, No. 8
tract and much higher results t h a n t h e precipitation method. If the method gives equally good results in the hands of other workers, then i t would be advisable t h a t fluidextract of Podophyllum, U. S. P., be assayed and standardized. As good lots of Podophyllum drug contain j per cent of resin, a standard of j per cent resin for the fluidextract is suggested. T h e method can also be applied t o t h e assay of solid and powdered extracts of Podophyllum by dissolving weighed quantities of t h e extracts in sufficient alcohol t o render t h e solutions of about t h e same strength as fluidextract. ANALYTICAL DEPARTMENT PARKS,DAVIS& Co., DETROIT
LABORATORY AND PLANT STUDIES ON FILTRATION’ By J. W. BAIN AND A. E. WIGLE
I n connection with factory operation quite recently, one of t h e authors had t o form a n estimate, in advance, of t h e amount of moisture which would be retained by a finely divided solid on a vacuum filter. A search among t h e usual sources of information yielded no serviceable data. When t h e filters were in actual operation, their performance in this respect was very much better t h a n had been anticipated, and had this fact been known in advance some economy in construction might have been effected. With a view t o gaining information on this point, t h e authors investigated t h e literature a t their disposal, and with t h e exception of the interesting and valuable paper b y Hatschek,2 they were unable t o find any useful data. When t h e experimental work had progressed t o a certain extent, an accident drew our attention t o t h e exhaustive monograph of King and Slichter, “ Principles and Con’ditions of t h e Movements of Ground Waters,”3 from which we have drawn freely in this discussion. I n t h e problem which is here under investigation, the solid is assumed t o be bathed by a liquid in which it is insoluble, such as, for instance, t h e mother liquor of a crystalline magma. It is proposed, therefore, t o investigate t h e amount of liquid retained by a mass of finely divided solid when filtration is carried out under atmospheric or other pressure and also in the centrifuge. The experimental work was considerably simplified by t h e condition laid down above, which permitted the use of a solid insoluble in water. A quantity of pure well-rounded lake sand was carefully sieved, and t h e grains which were retained on t h e 4 0 mesh screen b u t which passed the 30 mesh, are referred t o throughout as 40 mesh sand. The screens used were not of very good quality in t h e regularity of t h e mesh opening, as will be seen from t h e data given later, but this point is of no particular significance in this investigation. 1 Presented at the 6th Semi-annual Meeting of the American Institute of Chemical Engineers, Troy, New York. June 17-20, 1914 2 J . SOC.Chem I n d . . 1908, p . 538. 8 Nineteenth A n n Report, U.S. Geol. Survey.
The rate of flow of a given liquid under a constant head through a filter-mass of a finely divided solid will obviously be dependent upon the amount of space which is not occupied by the grains, i. e., what is commonly called the “pore space.” On first consideration, i t would appear t h a t t h e pore space would vary a good deal according t o t h e size of t h e grains composing t h e mass, and t h e results of computation and experiment are an astonishing contradiction t o this idea. The pore space is almost independent of t h e size of the grains, and the arrangement of t h e latter is of chief importance. By considering a number of small spheres of uniform diameter packed as closely as possible in a given space, it is possible t o arrive a t a mathematical formula from which t h e pore space may readily be calculated. Slichterl has shown t h a t if t h e spheres are so arranged t h a t their centers lie a t t h e corners of a cube, the pore space will be 47.64 per cent; while if t h e centers of t h e spheres lie a t t h e corners of a rhombohedron which permits t h e closest possible packing, t h e pore space is 2 5 . 9 5 per cent. Between these limits we may expect t o find the porosities of all ordinary materials. With actual materials, in t h e case where the grains are of approximately equal size,. t h e pore space and also t h e diameter of t h e particles may be readily determined b y counting a number of the grains, determining their combined weight and the specific gravity of t h e material; t h e total volume may be ascertained b y adding the sand in small quantities t o a cylinder, tapping gently with a flat-faced pestle until no further decrease in volume takes place. The results of this procedure on our sands are presented in Table I. Mesh screen
No.,of grains
30 40
(400 ,,,
50
{%I
60
80
{:E {igg
TABLEI Total One grain Sp. Pore space Diam. wt. grm. grm. X 10-6 gravity per cent Mm.
::;:::
2.74
~3 5 . 4 ~0 . 4 2 0] 34.1
0.354
E;:; :;:I
2.68 2.73
36.4
0.318
0.0238 o,0172 o,0156 0.0202
2.82 2.85
36.8 37.7
0.269 0.257
o,0253 0.0251
~
2:; ] ::) :;)
~
:
The comparatively slight variation in pore space 1
LOG.cit.. p. 309.
