I s I)
891,
~ 1 s .11rI
4 I.
.IN 1) E U G I N E I’: ii I N G
iii Figure 3. Since ut,ilieatioil of the polyhalite deposits must involve a large amount of engineering proccw developineiit in addition to tlic research work already done by tlic Bureau of Minrs, it might be argued that this potash mineral has no significance otiicr t1ia.n as a reserve for the iiidefinitr: fiiture when the sylvinite deposits liave lieen exhaustd. T l i ~writer it that a rather different amwer is
b
3 D
B
0
t 1
8 4 >
~. . . .
!i
FiGunE 1.
~RODti,:rlON A N D IMPow1.S OF POTASH Foll FEtil.IISEF:H 1N UNl?.IIO STATES
indicated, iind that poiyhaiite, altliongh admittedly less iniportmt than sylvinitc as a source of fertilizer potasli at tiic present time, liss an imrrietliate place to fill in tlie American potash industry. This point of view is based upon twu existing conditions: (1) a very constant demand in tlie Cnited States for a definite amount of 90 per cent potassium sulfate,‘ and ( 2 ) the lack of any appreeiable American production of t,his material. D k h T E 8 &fAKKET YON PO1’AsS:UM S1;LB’Al’t:. \\-bile the muriate of potash (80 per cent XCI) and lower-grade salts, which are also essentially chlorides, comprise liy far the greatest p r t i o n of tlie potash used in fertilizers in the United States, this condition is a result of the general availability of the German and B1sat.ian chloride deposits and tiicir ease of refinenlent rather than of any particularly desirable attributes of potash in the forni of chloride. In the case of tlie majority of CIO~JS it would lie iiiirnaterial whetlier the potash vere supplied in the fwni uf chloride, siilfatc, or some d h e r salt. However, eertain crops, such as tobacco, require a low-chloride material, creating a demand which has been satisfied by potassium sulfate as the salt other than the cliloridt~ most easily produced b>r the German piitash industry. I’otassiuln sulfate has imne to base an estahlished plnce in the fertilizer industry. There is a possil~ility,however, that its place might betakenbyother componnds, sncli aspotassiilm nitrate or phosphate. I n the subsequent considoration uf the place of polyhalite in the American potash industry, this possibi1it.y must he kept in mind. Tile factors wliich favor t,he sulfate are the long and satisfactory eqierience in its use and tlie possibility that the conibiried sulfur is also a necessary, though minor, fertilizer constituent. The consumption of pot.assium sulfate in the United States since 1021 may lie estimated from the imports, as shown grapliicaily in Figure 4. For the t h e years 1928-30, inclusive, an average of 47,000 short tons of potassium oxide was imported as the su1fat.e. In additioii to this, an indeterminate amount of “sulfate-muriate” refined froin molasses-distilleryresidues at Baltimore, Md., was sold. The 1
Cornmuiiiy iefrrred t o in tho fertiliper trade BR sulfate of putash.
c ii fi: 11 I S T R \i
Vol. 24, Yo. ti
figure of 17,000toils uf put.>Esiuin~sidf:per year as sulfate may be taken as a good estimate of noriiial demand. Tliisquarrtity is only about 13 per cent of the total fertilizer potash coiisunilition in the United States during JO2&30; hut xlicn it is considered that potassium sulfate comnrands a quoted-price difference over the muriate of $11 per ton of salt, or a1iproxiniately $0.25 per unit of p o ~ d ~ S i U I loxide, 1 this definite (leinand is sienificant. Tlie markets fur potassium sulfatc ( 2 7 ) in tlie cuiitinmt,al United Statcs are largely in Florida a i d California, n.1iere the sulfnt? is prefwred for the fertilization of citrus fruits, and in t,hc states (if the South Atlantic (’riast, from Ma Georgia, wlrere low-chloride material is preferred io These markets might offer an opportunity for considerable expansion if t.he sulfate were availaide a t a decreased price level. Export has not been eonsideritd, alt.horigli it niight be economically feasible. 2bIEEICAN SOURCES OF PO.l’ASSiU\l SU1,k’ATE. It SCelliS ~~ossilile that the potassium sulfate no\%required i n the United States, as well a any probable future increase in cr~iis-oniptiou, may he supplied by the treatment of pol>’nalite more wmomically than it may be imported from Europe or priidiieed from any other American source of potash. Wliilc thi. conii,ariron of probable cost figures for a nonexistent industry ivitli corresponding values for a foreign industry which is not i n c h e d to reveal its economic status is admittedly an exercise i n imagination, it appears froin tlie detailed estimates of Wroth (28) that the manufacturing cost of pota,ssium sulfate from po in the Texas-New Mexico region would he sliglit,ly 1 that for the best German operations. This qilestion of costs must be left open for tlre present but, if it is graiitrd, the question that remains is whether tlie sulfate or some t~qoally satinfactory salt of potash may be produced more clieaply from any Ami:rican source other than polylialite.
The possible sources of potassium sulfate in tlie United States are limited. In addition to the indeterniinat,e amount of sulfate material derived as a by-prodirct froni molasses distillation, there is a potential supply in tlie form of flue dust from cement kilns and blast fiirnat:es, although recent euperimental work by Madorsky (7) at the Bureau of Cheiuistry arid Soils has concentrated on the volatilization a i d recovery of potash as thc chloride. Volatilieation processes are not in use for actual potash production at present,, although tliey would heeorrie important in an eniergenry. Tlie pr(idoctirnr (if the sulfate hy solutiiin processes from various potash h as a1unit.e or greensand, is also a possibility, s does not S P P ~very promising as a. soilwe of
August, 1932
I N D US TR I A L A N D EN GI NE ER I N G CH E MI ST R Y
897
The production cost for potassium sulfate from muriate of large quantities of potash. The most probable large sources of American potassium sulfate are refined potassium chloride potash by the acid process in Alsace is believed to be somederived from Searles Lake or from the Texas-Kew Mexico what above the German cost which, in turn, is higher than deposits, and polyhalite from the latter region. The only that estimated for the production of potassium sulfate from other forms of potash which might conceivably displace the polyhalite (28). KOestimate can be rnade for the Hargreaves sulfate are the phosphate or the nitrate. A t this point a process but, if the marked increase in rate of reaction obtained brief survey of the more promising processes for the produc- by Britzke, Volkorich, and Kamenskaya ( 1 ) using inexpensive catalysts could be realized industriallv, an attempt to surtion of potassium phosphate, sulfate, and nitrate is in order. mount-the mechanical diffiPRODCCTION OF POTASSIUM culties inherent in the process PHOSPHATE. The most remight be justified. It does cent work on the siniultanenot seem probable, however, ous volatilization of potash that either the acid or the and phoqphorus from a mixHargreaves p r o c e s s would ture of a potash silicate with yield potassium sulfate a t a p h o s p h a t e rock is that of lower production cost than Hignett and Royster (h),who the German process involvused a small blast furnace. ing solution and recrystallizaThis type of process m-ould be tion, unless rather considerapplicable only where the two able value were assigned to minerals and a satisfactory the by-product hydrochloric blast-furnace fuel c o u l d be a c i d . If t h e a c i d o r t h e brought together a t low cost. H a r g r e a v e s p r o c e s s were The Green River Valley of to be used i n t h e U n i t e d Wyoming appears to be the States, it would p r o b a b l y logical location. Hignett and be d e s i r a b l e to ship highRoyster estimate that a large grade refined potassium chlofurnace burning 750 tons of ride from the potash sources coke per day could produce to a conversion plant located potash at a cost of $18.25 per advantageously with respect ton of potassium oxide if a to a supply of sulfuric acid value of $40 per ton were asor sulfur dioxide, an outlet signed to the P205recovered. f o r hydrochloric acid, While the potassium phosand the market for potasphate produced would be a sium s u l f a t e , rather than concentrated f e r t i l i z e r maattempting to produce poterial, the t r a n s p o r t a t ion 2. LOCATION OF GOVERNMENT TESTHOLESDRILLED t a s s i u m s u l f a t e either a t charges per unit of plant food FIGURE IN TEXAS-NEW MEXICO POTASH REGION Searles Lake, Calif., or Carlsto the present chief market bad, N. Mex. alone: the south Atlantic coast would still be very high. Although potassium phosphate As far as the writer is aware, no’ effort has been made to might find a growing market in the great interior agricultural convert the muriate of potash produced a t Searles Lake into regions, it does not seem probable that it would be competi- potassium sulfate, in spite of the market for the latter product in California, nor has the price difference of $11 per ton between tive with the sulfate in the present markets for the latter. PRODUCTION OF POT.WSIUM SULFATE AX11 POTA4SsIU&l imported muriate of potash and potassium sulfate inspired any American concern to convert the former into the latter. This XITR.4TE FROM POT.kSSIChf CHLORIDE. Most O f the potassium sulfate consumed in the American fertilizer industry is pro- circumstantial evidence might be interpreted to mean that the duced in the Crerman potash plants by a process involving the German process for potassium sulfate is economically superior use of refined potassium chloride and kieserite ( MgSOI.H20), to the acid process, and that potassiuni sulfate from polyhalite the latter material being found associated with the potash would be an economically sound proposition if it could meet deposits. By a two-stage process involving the intermediate German production costs. At the present time potassium nitrate is not a factor in the formation of a double salt of potassium sulfate and magnesium sulfate, potassium sulfate is produced with a theoretical yield potash market. As a simultaneous source of both potash and of 65 per cent (6). The mother liquor, rich in potassium nitrogen, it would be an attractive constituent in the manuchloride and magnesium chloride, is utilized in an associated facture of a highly concentrated fertilizer. If the trend operation for the recovery of potassium chloride from carnallite. toward more and more concentrated fertilizer continues, the Low sodium chloride in the potassium chloride and kieserite process for producing potassium nitrate by the reaction beused as starting materials is a requisite. tween nitrogen peroxide and solid potassium chloride While the German industry has a sulfate material readily described by Whittaker, Lundstroni, and Merz (26) will available in its potash deposits, usable sulfates are lacking in undoubtedly be investigated on an industrial scale. I t is other potash regions, such as those in Alsace and a t Solikamsk possible that potassium nitrate might be produced by such a in the Union of Socialist Soviet Republics. The Alsatian in- process a t a cost which would make it competitive with dustry has accordingly utilized sulfuric acid, while the Russians potassium sulfate. In fact, in considering the utilization of have recently (1)followed an earlier German lead (3)in attempt- polyhalite from a long-range viewpoint, the potential producing to adapt the Hargreaves process to the production of potas- tion of potassium nitrate from potassium chloride seems to the sium sulfate. In either case it is necessary to dispose of the by- writer a more serious factor than the actual production of product hydrochloric acid which is obtained in the theoretical potassium sulfate from potassium chloride. ratio of 0.42 pound per pound of potassium sulfate. A For the present, it seems possible that potassium sulfate may new Alsatian plant is recently reported as using this hydro- be produced at a lower cost from polyhalite than from sylvinchloric acid for the production of superphosphate (24). ite. A number of different processes suggested for the treat-
-
I
8911
u
11 11s
’r ii I .4 I, r. u u
ii
N G I N E FC
inent of polyhalite arc diaaussed briefly in tlie following section.
P+hnh/e
XSO
$ 28 u>
H d tP
0 Nor/
Anhl&,,.-
CoSO,
Mognes,te
MgCO,
0!her/mpunrw &JIJ2 y,sl
--
,2 9
82
07
2.3
HI
u G c H E M I s ‘r 11 Y
Vol. 2-1, No. 8
decrease, owiiig to the reformation of polyhalite. Tlie eneineerine nrobleni is to so control the variables in the extrac-
iiiagnesiuni sulfate is obtained, since tlie calcium sulfate concentration is only of tlie order of 0.3 gram per 100 grams water. In practical operation it will probably be difficult t,o exceed a cmrentration of I1 grams potassium sulfate per 100 g r a m water in tlie extract liquors, which will also contain somewhat more than the equivalent concentration of 7.6 grains iriagncsiuiii sulfate per 100 pains water. By subseqiicnt evaporation and rrystalliaation steps based on equiIilriurn data for the potassium sulfate-magnesium sulfat,e-
Partridge (2) detraction and evaposcribes a process difration of tlie extract fering radically from liquors. any h i t h e r t o proIf a dilute potassium sulfate s o l u posed. tion is used in place CALCINATION AXIJ of w a t e r to r e a c t HOT ESTHACTION. with calciiied polyOwing to the slow ha1it.e in the cold, rate of solution and syngenite v i t h o u t low concentration of a d m i x e d gypsum potassium s u l f a t e may be o1)tained as ohtained when polytlie solid product. halite is extracted This complete cond i r e c t l y with hot version of tlie calwater, most of the cium sulfate content processes proposed of polylialite iiito i n v o l r e an initial syngenit.e is a basic calcination of polyoperation in Bureau halite, as first deof Mines process 4 scribedbyRose(l0). a n d i t s inodifice This r e m o v e s the 1mt:er of hydration t.ions. Details conGns-Fiirm ROT.&RS KILN AND PnnT OF E~TRACTIOX E Q U I P X ~,%T NT eerning processes 4 and apparently 1’0)TASH RESEhnCll h I I 1 i R A T O R Y and 5 are gir.en by b r e a k s d o w n the Rtoreh and Fragen c o m n l e x salt into the Lonstituent sulfates. On subsequent hot extraction, in recerit Publicatioris ( I X , 1s)). Syngenite has some possibilities of its own as a potassium potassium sulfate, magnesium sulfat,e, and raleiilm slllfate all go into solution, the concentratioli of calcium sulfate, . sulfate material for fertilizer, since i t contains approximately however, being very low relativc to the concentrations of 29 per cent potassium oxide when pure. REXOV.XOR MAGNESIUM BY MEANSOF LIME. Iii processes potassium sulfate and magnesium sulfate. During batch ext.ract.ion these concentra.tions attain a maximum and then previously mentioned, calcined polyhalite mas extracted hot ~~~
August, 1932
I N D U S T R I A L A"ND E N G I N E E R I Y G C H E M I S T R Y
to yield a solution rich in potassium sulfate and magnesium sulfate, and potassium sulfate and schonite were recovered by evaporation and crystallization steps. An alternative method of treating the potassium sulfate-magnesium sulfate extract is precipitation of magnesium hydroxide with lime, followed by recovery of the potassium sulfate from solution by evaporation. This is specified in Bureau of Mines process 3 (17). A French patent to the Standard Oil Development Company (14) and an American patent ( 8 ) , which is apparently a translation of the former, specify the use of lime in a different manner to eliminate magnesium from the extract solution. According to these patents it is possible to dispense with the calcination of polyhalite and still obtain rapid extraction if lime equivalent to the magnesium content of the polyhalite is mixed with the latter ground to pass a 60-mesh screen and if the mixture is digested with hot water. REhfOv.4L O F hfAGNEsIUM A S D C.4LCIUJf BY hfEANS O F A-\I>iom4. ~ X DCARBOSDIOXIDE. Another method of extraction, intended to reduce not only the magnesium but also the calcium concentration of the extract liquor, was investigated by Hill and Adams ( 5 ) a t the Fertilizer and Fixed Xitrogen Laboratory of the Bureau of Chemistry and Soils. Using ammonium carbonate solutions both with and without an excess of ammonia, they were able to extract potash from uncalcined polyhalite a t room temperature. When an excess of ammonia was used, the magnesium content of the extract was held to a low value, but so also was the potash concentration. Using ammonium carbonate solutions with no excess of ammonia, potassium sulfate concentrations of about 10.5 grams per 100 cc. were obtained for initial ammonium carbonate concentrations of from 18 to 22 grams per 100 cc., but less than half of the magnesium corresponding to the potash was removed from solution. A different and apREDUCTION AND HOT EXTRACTIOX. parently promising method of separating and recovering the potash content of polyhalite is reported by Fraas and Partridge ( 2 ) . In its simple details this consists of the reduction of polyhalite by means of hydrogen, and hot extraction of the residue with water. The potash in the reduction product is almost completely extracted, while practically no magnesium or calcium goes into solution. A very concentrated extract may be obtained which, on evaporation to dryness, yields a sulfide product containing more than 50 per cent potassium. On fusion to drive off additional water, the potassium content is increased to 64 per cent, equivalent to 77 per cent potassium oxide. OTHERPROCESSES. It is believed that all of the polyhalite processes cited in recent technical and patent literature have been mentioned in the preceding sections. These processes do not, however, exhaust the possibilities. Investigation of additional lines of attack is being continued by the Bureau of Mines simultaneously with further research on those processes already proposed. POSSIBLE BY-PRODUCTS FROhf POLYH.4LrTE When Wroth (28)concluded that potassium sulfate could be produced from polyhalite by Bureau of lMines process 1with a total manufacturing cost slightly below the best German practice, he made no allowance for revenue from by-products. Although the Texas-Yew Mexico potash deposits are remote from general commodity markets and from water transportation to these markets, the chance of developing economically significant by-products should be considered. Some of the possible by-products are briefly mentioned in the following sections. CALCIUM SCLFATE. In all processes involving hot extraction of calcined polyhalite without addition of chemicals during extraction, it will be necessary to dispose of a large amount of calcium sulfate obtained in the form of a sludge. This
899
calcium sulfate comprises not only that combined in the polyhalite to the extent of 45 per cent of the weight of this mineral, but also any anhydrite present as an impurity. The actual sludge will be largely gypsum and will be contaminated with small amounts of iron oxide, clay, and magnesia, in addition to anhydrite. Calcium sulfate containing considerable quantities of magnesium hydroxide would be obtained from processes involving lime treatment during extraction, but the recovery of this calcium sulfate would scarcely be feasible.
FIGURE 4. POTASH MATERIALS IMPORTED FOR FERTILIZER
The most obvious outlet for the calcium sulfate residue would be in the manufacture of plaster or plaster products. It is possible that the red color of the material might be turned to an advantage if it could be standardized, but the distance from any considerable market and the well-developed state of the gypsum industry render its utilization doubtful. MAGNESIUM SULFATE.The waste liquors from all processes in which calcined polyhalite is extracted with either hot or cold water without addition of precipitating chemicals will contain a high concentration of magnesium sulfate and low concentrations of potassium sulfate, sodium chloride, and calcium sulfate. It should be possible to recover magnesium sulfate as Epsom salts (MgS04.7Hz0) by evaporation and crystallization if there were any market for this commodity. This recovery of Epsom salts has been mentioned by Schoch in two of his patents (12, I S ) . SODIUMSULFATE.The waste liquors high in magnesium sulfate would also serve as a source of sodium sulfate by low-temperature reaction with sodium chloride. The latter might be obtained partly by using the waste liquors to wash salt from the polyhalite going to the main process, and partly from salt mined from the extensive deposits with which the polyhalite is associated. Since the kraft paper industry has shown a marked movement toward the Gulf Coast in recent years, it might be possible to develop a market in this region for sodium sulfate produced in conjunction with potash recovery from polyhalite. This possible by-product must meet the competition of established industries which produced the following products in 1927 ( 2 3 ) :
August, 1932
I ZD U S T R I A L A S D E N G I N E E R I N G C H E M I ST R Y
manufactured in the German potash plants or than it might be made in this country from potassium chloride, and such an industry seems assured of a definite and steady market for close to 100,000 tons of 90 per cent potassium sulfate per year. The potential significance of potassium magnesium sulfate and of syngenite as potash fertilizer materials must not be neglected in considering the status of polyhalite. One or the other of these may be produced in many of the processes mentioned in this paper, although their manufacture has not been stressed. Potassium magnesium sulfate is already used for soils deficient in magnesia, while syngenite might be competitive with manure salts. The potassium oxide contents of polyhalite and of the products which might be derived from it are compared graphically in Figure 5 with those of standard potash materials. The development of the Texas-Kew Mexico potash deposits has been aided by the establishment of a freight rate of $5 par net ton on potash salts from Carlsbad, N. Mex., to Rouston or Galveston, Tex., for coastwise or export traffic. The water haul to Atlantic Coast ports will add approximately $2.50 to the transportation costs. Using !A7roth's value of $16 for the total production cost of 90 per ceiit potassium sulfate from polyhalite (29),the cost of production plus transportation to dtlantic Coast fertilizer plants may be estimated a t $24 per ton. The margin of $18 between this value and the actual selling price of German potassium sulfate in the United States after allowance of the maximum discount seems large enough to make the proposition Tvorth continued study.
ACKNOKLEDGJIEUT The thanks of the writer are due to all of the members of the Bureau of Mines Potash Research Laboratory for critical review of this paper, and to A. H. Emery for assistance in procuring information.
LITERATURE
901
CITED
(1) Britzke, Volkovich, and Kamenskaya, I'dobrenie i Crozhai, 2, 492-5 (1930). (2) Fraas and Partridge, I N D . ENG. CHEar. (in process). (3) Hepke, -Iltt2. Kali-Forshungsanstalt, 1919, 13-28. (4) Hignett and Royster, IND. EKG.CHEX, 23,84-7 11931). (5) Hill and Adams, Ibid., 23, 658-61 (1931). (6) Krull, Kali, 12, 347-56 (1918). (7) ,Madorsky, IND.EVG. CHEU, 24, 233-7 (1932). ( 8 ) Ransom. U. S. Patent 1.812.497 (June 30. 1931). (9) Robertson, IKD.ESG. CHEM.,21, 520-4 (1929). (10) Rose, Ann., 43, 3 (1854). (11) Schoch, U. S. Patent 1,794,551 (March 3, 1931). (12) Schoch, U. S.Patent 1,794,552 (March 3, 1931). (13) Schoch, U. S.Patent 1,794,553 (March 3, 1931). (14) Standard Oil Development Co., French Patent 661,278 (March 4, 1929). (15) Starrs and Clarke, J . P h y s . Chem., 34, 2367-74 (1930). (16) Starrs and Starch, Ibid., 34, 1058-63 (1930). (17) Starch, ISD. ENG.CHEM.,22, 934-41 (1930). (18) Starch and Fragen, Ibid., 23, 991-5 (1931). (19) Starch and Fragen, Bur. Mines, Repts. Investigations 3116 (Sept.. 1931). (20) Teeple, "The Industrial Development of Searles Lake Brines with Equilibrium Data," .2. C. S. Monograph 49, Chemical Catalog, 1929. (21) Tyler, Bur. Mines, Circ. 6406 (Feb., 1931). (22) Tyler, Ibid., 6437 (May, 1931). (23) U. S. Census of Manufactures, 1927. (24) U. S.Dept. of Commerce, World Trade .Votes o n C'hemicala and Allied Products, 6 , No. 3 (Jan. 18, 1932). (25) ti, S. Potash Co., private communication. (26) Whittaker, Lundstrom, and Merz, IKD.ENG.CHEW., 23,1410-13 (1931). (27) Wroth, Bur. Mines, BUZZ. 316, 23-30 (1930). (28) Wroth, Ibid., 53-119. (29) TTroth, Ibid., 105. RECEIVEDMarch 15, 193%. Presented before the Division of Industrial and Engineering Chemistry a t the 83rd Meeting of the American Chemical Society, New Orleans, La., March 28 t o April 1, 1932. Published b y permission of the Director, U . S. Bureau of Mines. (Xot subject t o copyright.)
Effect of Storage on Pyrethrum Flowers c. B. (:;NQDIKGER
P
AKD
C.
s. CORL, McLaughlin
YRETHRUM flowers are harvested in May and June in the countries which produce them cornniercially. Shipments from the new crop begin to arrive in the L-nited States in August and September. The latter month marks the end of the insecticide season in this country. It is obvious, therefore, that the pyrethrum crop of a given year cannot be used against insects until the following year; frequently flowers are carried over for a second year before reaching the ultimate user. It has been recognized that long periods of storage may result in decomposition of the active principles, but until recently no method was available which was sufficiently accurate to determine the extent of the loss of pyrethrins. Earlier investigators were obliged to depend on biological tests of a type now known to be too inaccurate to detect the changes that occur. Most of the pyrethrum imported into this country is used in manufacturing liquid insecticides of various kinds. For this purpose the coarsely ground flowers are employed because the impalpable powder, so widely used for dusting ten years ago, is not suitable for percolation or extraction. The ground flowers are ordinarily packed in 100-pound burlap hags and in slack barrels holding 150 to 200 pounds; in either case, plain or waterproof paper liners are used. The difference between the ground and powdered flowers is shown by the following typical screen analyses:
Gorrnleg King Company, hlinneapolis, J h n . G R O L \ I D€ O R Retained Retained Retained Retained Retained Retained Through
PERCOL4TIOV
on 30-mesh sieve on 40-mesh sieve on 60-mesh sieve on 80-mesh sieve on 100-mesh sieve on 120-mesh sieve 120-mesh sieve
(GFP) 76 2.6 13 7 38 5 11 2 11 2 6 1 16 7
FI\E POBDER
70 Retained on 100-mesh sieve Retained o n 200-mesh sieve Through 200-mesh sieve
0 40 60
Both ground and powdered Japanese and Dalmatian Pyrethrum cinerariaefolium were used for the experiments described in this paper.
EXPERIMENTS o s GROUSDFLOWERS Three hundred kilograms of Japanese pyrethrum were ground on a commercial mill at a temperature less than 40' C. The ground material was thoroughly mixed, and part of it was packed in 500-gram containers of the following types: open metal trays, unlined burlap bags, vacuum coffee cans, friction-top tin cans. The pressure in the vacuum cans was 380 mm. Six packages of each kind were prepared so that an unused package was available for each analysis. In addition, a slack barrel, burlap bag, fiber drum, and metal drum, representing the different commercial packages, were filled with the ground flowers. All of the containers were stored at a temperature of 26" to 30" C. in a modern concrete factory building and were not exposed to direct sunlight. -4 composite sample, consisting of equal amounts from each
