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
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Vol. 6, No.*j
because of t h e parcel post development, t h e growth of trolley lines, a n d freight a n d automobile trucks. However, industrial growth will depend o n cheap railroad rates for fuel a n d raw materials a n d for shipment of finished products t o a degree which will make t h e other means of transportation hardly worthy of consideration. On t h e other hand, there are certain characteristics in rural locations which are attractive for industrial enterprises. T h e cost of sites for factories a n d residences of employees, t h e ability of workingmen t o have their own gardens, t h e facility for waste disposal, can, if t h e fundamental conditions be made right, work a practical revolution. B u t transportation conditions are t h e vital point a n d t h e scheme will be impracticable until t h e rural point can be guaranteed t h e same transportation rates as t h e city. W. A. H A U O R
planned t o bring t o chemists a n d engineers prompt notice of all government reports of interest t o t h e m , a n d t o briefly a n d clearly review t h e scope a n d purpose of these publications. It is not intended t h a t t h e articles shall be fully abstracted, since the work of Chemical Abstracts in this line should not be duplicated; b u t a prompt announcement of t h e publications will do a great deal t o assist t h e chemical profession in taking advantage of t h e material now being issued by t h e Government. It will certainly be more convenient for t h e members of our Society t h u s t o have condensed into one list t h e announcements previously scattered through a number of lists appearing a t irregular intervals from t h e various departments. All Government Printing Office publications of va1,ue t o chemists will be reviewed, including those which have appeared since J a n u a r y I , 1914. T h e items of industrial importance appearing in the Daily Consular Reports will also be abstracted, beginning NEW SECTION ADDED TO JOURNAL with March I , 1914. A new section o n G O V E R N M E NPUBLICATIONS T It is our belief t h a t this up-to-date s u m m a r y of t h e has been added t o the J O U R N A L , beginning in this i m p o r t a n t investigations a n d publications of t h e issue, ,under t h e editorship of R. S. McBride, Associate Government will be of immense value t o our profesChemist in t h e Bureau of Standards. This work is sion.
I
I
.ORIGINAL PAPERS
STUDY OF THE COMPOSITION OF WATER GAS TAR
.
By C. R . DOWNS A N D A. I,. DEAN Received February 17, 1914
Water gas tar, more properly carburetted water gas tar, is t h e t a r r y product separating out in the purifying systems of plants manufacturing carburetted water gas. It is much less viscous t h a n ordinary coal t a r , with a distinctly different odor, due in part t o t h e absence of t h e phenols a n d bases characteristic of coal t a r . It is understood t h a t a portion of t h e petroleum used in carburetting, after passing through various molecular changes, appears finally as t a r , b u t of t h e exact nature of t h e transformations little is definitely known. It is, of course, the object of t h e gas maker t o change as large a percentage of his gas oil into permanent gases as possible a n d keep t h e production of t a r t o t h e lowest limit. A search through t h e literature for d a t a concerning water gas t a r yields b u t fragmentary a n d inadequate results. A. H. Elliott,‘ Matthews a n d Goulden,Z a n d C. N. Forrest3 have recorded t h e results of fractional distillations of t h e t a r , a n d Dean a n d B z ~ t e m a nS. , ~ P. S a d t l e ~ - ,a~n d Forrest3 have furnished information regarding t h e composition of the creosote oils derived f r o m water gas tar. Some of the statements t o be f o u n d in t h e literature refer t o material clearly quite different from t h e water gas t a r produced in t h e standard American installations of t h e present day. T h u s Matthews a n d Goulden’s t a r was lighter t h a n water a n d contained 8.51 per cent of “light paraffins.’’ Am. Chem. Jour., 6, 248. Gas W o v l d . 16, 6 2 5 . *Jour. SOC.Chem. I n d . , SO, 193. U.S . Forest Service, Circular 112. 6 Trans. A m . I n s l . Chem. Eng.,2, 177. 1 2
T h e d a t a presented in this paper were obtained on water gas t a r from t h e p,urifying system served b y several standard Lowe system water gas sets. T h e carburetting oil in use a t t h e time was derived from Oklahoma crudes. As might be predicted, t h e t a r separating a t different points along t h e purifying system, as t h e gas passes from t h e sets t o t h e final stages of purification, becomes p r o g r e s sively lighter a n d richer in t h e more volatile constituents.l M i x e d t a r f r o m t h e whole system was used for t h e work described in t h e present paper. S Y S T E M A T 1C
TIONAL
F R A C-
DISTILLA-
TIONS
A series of detailed fractional d i s t i l l ations was carried out with a view t o locating t h e boiling points of a n y indiFIG.I - C H A M B E R S OF DEPHLEGMATOR v i d u a l compounds A, PERFORATED GLASSPLATES B , SIPHON TUBES which might be present in substantial amounts. T h e first distillation of the t a r up t o 2 5 0 ’ C. was carried out in a five gallon 1
Dean and Downs, THISJ O U R N A L , 3, 108.
May, 1914
T H E JOUR-VAL OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
copper still, t h e distillation being effected b y immersing a resistance coil i n t h e t a r . T h e distillates t h u s obtained constituted t h e “First Series” of fractions, a n d t h e
367
common practice of handling t h e fractions in such work, was continued t o t h e “Third Series” of fractions boiling u p t o z 5 0 c C. and t o t h e “Sixth Series” with t h e lower boiling portions. The curves of t h e third a n d sixth series are shown in Figs. z a n d 3. F r o m Fig. z i t is clear t h a t t h e largest single constituent boils a t about 2 2 0 ’ C.. approximately t h e boiling point of naphthalene. The abrupt rises in Fig. 3 a t Soo, 1 1 0 ’ and 140’ C. indicate t h e presence of appreciable amounts of individual substances boiling near these temperatures, which were subsequently proven t o be benzene, toluene. a n d t h e xylenes. A smaller irregularity appears near t h e boiling point of mesitylene, 1 6 4 . j ’ C. It is believed t h a t a fairly satisfactory separation had been achieved in this sixth series, and during considerable portions of t h e distillation when t h e distillates appeared t o be nearly pure compounds, fractions were taken a t each degree rise i n temperature a n d corrections made for the emergent thermometer stem. GENERAL CHARACTERISTICS O F THE DISTILLATES
INDICES O F REFRACTIOK-The indices of refraction of t h e fractions of t h e fifth series were determined at 30’ C. with t h e results shown in the following table: Temp. of fraction
= I k . 2-THIRD
S E R I E S DISTILLATIOS
residue was saved for later study. These first fractions were then refractioned from a n electrically heated glass flask provided with a Hempel column, yielding t h e “Second Series.” I n refractioning t h e second a n d subsequent distillates a modified Young dephlegmator was employed u p t o zooo C.. a n d above t h a t t h e Hempel column. This Young dephlegmator consisted of six chambers, t h e floors of which consisted of perforated glass plates provided with overflow tubes as
c.
79- 83 83- 85 85- 90 90- 95 95-100 100-109 109-113 113-1 15 115-120 120-125
Temp. of fraction
1 ,4938 1 ,4938 1 ,4933
125-130 130-137 137-145 145-150 15&155 155-160 160-165 165-172 172-179 179-185
1 ,4923 1.4921 1.4910 1 ,4909 1,4910 1 ,4908 1.4912
c.
Refractive index a t 30’ C. 1.4916 1 ,4935 1 ,4967 1 ,4987 1.4976 1.4968 1.4979 1,5030 1.5180 1 ,5269
BROMISE ABSORPTIOS
The bromine absorptions of t h e fractions were used a s a relative measure of t h e unsaturated hydrocarbons. The determinations were made b y allowing a n excess of a t e n t h normal solution of bromine in carbon tetraSixth series fractions
c.
indicated i n Fig. I . T o avoid escessive condensation in t h e chambers t h e dephlegmator was air-jacketed u p t o 1 1 0 ’ C.. a n d above t h a t enclosed in a n asbestos sheath heated b y resistance wires. I n this way t h e process of repeated fractionation, according t o t h e
Refractive index a t 30’ C.
78.9- 79.7 79.7- 8 0 . 7 80.7- 8 5 . 0 65.0- 9 2 . 0 92 -101 101 -109 109 -110.5 110.5-114 114 -120 120 -130 130 -138 138 -142.5 142,5-145 145 -150 150 -155 155 -160 160 -164 161 -167 16; -172 172 -177 177 -182
G. Br added Third series fractions per cc. c. 0.0133 0.0181 0.0133 0.0182 0.0192 0.0141 0.0104 0.0133 0.024i 0.0364 0 P67I 0.1098 0.1T24 0.2186 0.1832 0.1616 0 . I522 0.4176 0.4824 0.4008 0.5520
180-205 205-235 235 -250 Second series fractions 250-260 260-2 7 0 270-280 280-290 290-300 300-3 10 3 10-3 20
G. Br added per cc. 0.448; 0 2526 0 1629
0.0479 n. 0432 0.0610 0,0442 0.0963 0.0771 0,0;00
chloride t o react on I cc. of a sample for ~j minutes, t h e vessel containing t h e mixture being immersed in a b a t h of ice and salt a n d kept in t h e dark. After this
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
368
reaction period t h e unused bromine a n d t h e hydrobromic acid formed were both determined, a n d from these determinations t h e grams of bromine added per cubic centimeter of oil could readily be calculated. ( L
t
PARAFFINS”
Since t h e hydrocarbons of water gas t a r have their origin in petroleum oil it might be supposed t h a t considerable quantities of ‘(paraffins” would be found in t h e distillate therefrom. T o throw light on this point the fractions were sulfonated with concentrated sulfuric acid a n d the percentage by volume of the unsulfonated residues determined. Temp. of fraction Per cent Temp. of fraction 6th series Unsulfonated 6 t h series 75 - 79 79 - 90 80 - 81 81 - 85 8 5 - 92 92 -101 101 -109 109 -110.5 110.5-114 114 -120 120 -130 130 -138
0.06 None None None None h’one None None None None 0.4 0.4
138 -142.5 142.5-145 145 -150 1.50 -155 155 -161 161 -166.5 166.55172 172 -177 3rd series 180 -205 205 -235 235 -250
Per cent unsulfonated 1.2 2.4 1.2 2.2 1.6 1.8 1.6 I-one
THIOPHEX
T h e sulfur containing compound thiophen (C4HdS) appears t o be always associated with benzol in coal t a r light oil. Because of the closeness of its boiling point (84’ C.) t o t h a t of benzol, it cannot be removed by fractional distillation. T h e presence of thiophen in water gas t a r distillates was indicated by t h e indophenine test with isatin a n d concentrated sulfuric acid. The method of Denigssl was followed in making quantitative estimations of this compound. T h e average of thirteen analyses of the fractions between 79’ C. a n d 90’ C. was 2.1 per cent. Tests for the higher homologues of thiophen were obtained with t h e higher boiling fractions, b u t no quantitative estimations were attempted. Comfit. rend., BO, 781.
1. . . . . . . . . . . . . . . 68O- 79’ 2................ i9~-100~ 3 . . . . . . . . . . . . . . . 100°-1250 4 , . . . . . . . . . . . . . . 125 O- 155
1.4 2.2
LOW-BOILING F R A C T I O N On repeated distillation of the first fractions below 75’ C. a small amount of a very volatile liquid was obtained, boiling between 44’ C. a n d 65’ C., most of it coming over between 60’ a n d 6 2 ’ . So small a quantity of this material was obtained t h a t anything more t h a n a few qualitative tests was not feasible. It charred a n d left no residue of undissolved oil when treated with concentrated sulfuric acid. It reacted violently with strong nitric acid, a n d absorbed bromine rapidly from bromine water, forming a bromin a t e d product heavier t h a n water. N o test for sulfur could be obtained. These tests combine to indicate a hydrocarbon mixture of markedly unsaturated character .
1
BENZENE
An inspection of the distillation curve of t h e sixth series shows a decided rise a t t h e boiling point of benzene, indicating t h e presence of about 0.4 per cent of t h a t compound. T h e distillate between 79’ a n d 8 1 ” could be readily nitrated, giving a good yield of nitrobenzol boiling between 106.5’ a n d 107.5’ and showing no evidence of “paraffins” b y t h e method given b y Lunge.’ Dinitrobenzene, melting point 90 O, a n d aniline distilling between 1 8 2 ’ a n d 185’ were also prepared from the purified benzene obtained from water gas t a r . The aniline was colorless a n d turned only slightly brown on standing four months protected from sunlight. A number of samples were prepared conforming t o t h e requirements of t h e commercial grades of benzol. T h e starting material was a crude light oil obtained in the initial distillation of water gas t a r in a large still. This was fractioned up to 180’ C. from a large plain distilling bulb and t h e distillate refractioned through a Hempel column taking the following fractions:
55.0
T h e extraordinarily high percentage in the distillate from 180°-20j0 calls for some comment. T h e residues from all t h e other fractions were washed t o clear oils, b u t t h e material obtained here was of putty-like consistency a n d resinous odor, a n d appeared t o be a polymerization product of some unsaturated hydrocarbon rather t h a n a “paraffin.”
Vol. 6 , No. 5
Pure benzene was prepared from the fraction No. 2 b y agitating with concentrated sulfuric acid, followed by washing with dilute acid a n d water, a n d agitation with caustic soda solution followed by thorough washing. Under laboratory conditions a loss of 4 per cent was experienced by these treatments. T h e washed product was carefully redistilled with a Hempel column a n d Young dephlegmator, yielding a product of correct boiling point. This C. P. benzene gave no test for thiophen, no discoloration with concentrated sulfuric acid, was of sweet odor a n d has shown no yellowing on standing for two years. Preparations of 90 per cent benzol a n d 50 per cent benzol were also made from water gas t a r light oil b y fractional distillation a n d washing with sulfuric acid a n d caustic soda. With these products much less exact fractional distillation was required t h a n with the c. P. benzol. Both preparations were free from thiophen, gave no color with concentrated sulfuric acid, a n d have remained water white a n d sweet for two years. The loss in washing was small. I n preparing 160’benzol or solvent n a p h t h a t h e same general process of washing was followed but t h e loss in washing was much greater, amounting t o over 1 5 per cent, T h e product was of good color a n d odor, a n d gave but a very pale straw color with concentrated sulfuric acid. T 0 L U E NE
An inspection of t h e “Sixth Series” distillation curve shows a rise of about 0.8 per cent a t t h e boiling point of toluene. A portion of this fraction of t h e sixth series was nitrated, giving 8 j per cent of t h e theoretical yield, a n d showing b u t a trace of paraffins. T h e fraction No. 3 from the Hempel column distillation mentioned under “Benzene” above was washed with sulfuric acid a n d alkali (with a loss of 6 per cent) 1
“Coal T a r and Ammonia,” 3rd Edition. p. 641
,
May, 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 ENGINEERING C H E M I S T R Y
a n d t h e washed oil fractioned with a Hempel column. T h e fraction 9jO-120~ was redistilled with the same apparatus a n d t h e fraction 109.5 '-I I 1.5 taken. This product compared favorably with standard makes of c . P . toluene a n d gave no test for thiotoluene a n d no color with concentrated sulfuric acid. XYLENES
369
filtered off a n d pressed in a screw press; t h e filtrate was placed in a freezingmixture a n d thenewcrop of naphthalene crystals similarly removed; this filtrate was distilled collecting a fraction from 18j '-265 O 1 which was cooled, filtered a n d t h e naphthalene pressed; t h e new ' , filtrate was refractioned, taking a fraction 195'-23 j which was similarly deprived of its naphthalene a n d the new filtrate distilled, collecting a fraction 210'2 2 j o J which yielded but a very small separation of naphthalene when placed in a freezing mixture; t h e total weight of the solids thus recovered amounted t o 8.0 per cent of t h e tar.
,
T h e next decided rise in the distillation curve after t h a t a t t h e toluene fraction appears around 140', suggesting t h e presence of xylenes. T h e curve indicated about 1 . 2 per cent of these hydrocarbons. T h e separation of t h e three isomeric xylenes b y fracNaphthalene was prepared from t h e solids pressed tional distillation is not feasible because of the nearness from the distillate obtained from water gas t a r between of their boiling points. By t h e use of Levenstein's 2 0 0 ' a n d 2 j 0 ' . These solids were distilled, rejecting method' one sample of xylene fraction yielded 75 per t h e first and last I O per cent, a n d t h e distillate treated cent metaxylene, 20 per cent para, and, by difference, with sulfuric acid containing a little dichromate. The 5 per cent of t h e ortho. On another sample of water product, after thorough washing with water, was gas t a r t h e results were 7 7 per cent meta, 19.5 per cent pressed a n d distilled, giving a product boiling a t 2 I 7 ' C. para, 2.0 per cent ortho, a n d 1 . j per cent "paraffins." (uncorrected) a n d melting a t So', which showed no It is doubtful whether t h e ortho-xylene is present in discoloration with concentrated sulfuric acid a n d remore t h a n traces since a qualitative test2 failed t o mained perfectly white after a n exposure of four reveal its presence. months t o t h e light. T h e sodium salts of t h e ortho- a n d meta-xylene sulANTRRACENE furic acids were prepared according t o J a ~ o b s e n . ~ T h e needle-like crystals similar t o those described for T h e above described experimental work was carried t h e ortho salt were only present in very small amounts. out for t h e most part on t h a t part of t h e water gas t a r Metaxylene boiling 138'-139" was prepared according which distilled below z j o o C. in t h e initial distillation. t o Jacobsen b y decomposing t h e meta-xylene sulfuric The residue above 2 j O " C. was worked up in collaboacid. ration with Dr. F. L. Haigh of this laboratory. MESITYLENE Two methods of distilling this residue were tried; .A slight irregularity of t h e distillation curve around in one the distillation was carried out with heat alone, 16 j ' suggested t h e presence of mesitylene. T h e "Sixth in t h e other steam was introduced into t h e still in conSeries" distillate obtained a t this point was twice re- siderable volume. I n both types of distillation most distilled with a Glinsky dephlegmator a n d t h e distillate of t h e fractions showed a separation of solid materials between 164' a n d 167' nitrated. A solid nitro-com- on cooling. These solids were removed, pressed a n d pound was obtained which after careful washing a n d weighed a n d the anthracene in t h e m determined according t o t h e method proposed b y Meister, Lucius recrystallization gave a constant melting point of 236'. T h e nitration of another portion gave a product melting a n d Bruning,' ' I with appendix." This method conat 235'. Mulliken gives the melting point of trinitro sists in converting t h e anthracene into anthraquinone by treatment with chromic acid in glacial acetic acid mesitylene as 23 j " C. solution. T h e anthraquinone was further purified b y F r o m t h e alcohol used t o wash the crystals of trisolution in fuming sulfuric acid a n d recovery therefrom nitro mesitylene a small crop of barrel-shaped crystals was obtained which on repeated recrystallization gave by dilution. a melting point of 167', a n d contained 16.31 per cent T h e results of t h e dry distillation were as follows: of nitrogen. The theoretical nitrogen content of triPer nitro-trimethyl benzenes is 16.47 per cent, b u t the Per cent Tempera- Per cent Per cent cent of melting point is far too low for trinitro pseudocumene. Temperature solids ture of solids anthracene anthracene e C. in fractions in solids C. in fractions in solids T h e amount of this compound was too small for further -265 None 335-345 4.19 41. i 5 experiments, a n d it remained unidentified. .
S A P HT H A L E K E
Inspection of t h e distillation curve for the third series shows t h a t t h e most decided rise in t h e whole curve appears between 2 I j ' a n d 23 j O. indicating a relatively large proportion of naphthalene. An a t t e m p t was made t o estimate the amount of naphthalene in water gas t a r as follows: j o o grams of t a r were distilled t o 260' C. a n d t h e naphthalene separating in t h e distillate 1
Jour SOC.Chem. I n d , 4, 78.
2
Mullikrn, "Identification of Pure Organic Compounds," Vol. I. p. 202. Ber.. 10, 1009.
3
265-305 305-315 315-325 325-335
None 1.32 2.32 3.85
.
I
...
65.49 61.35 42.82
345-355 355-360 360-370 370-400
4.27 3.39 4.36 Sone
34.85 26.41 7.41
...
These results show t h e presence of 0.392 per cent of anthracene in t h e residue above z ~ o ' ,equivalent t o 0.29 per cent of the original tar. The thermometer readings in the steam distillation F e r e of little value; t h e fractions were accordingly cut a t about each 2 5 0 cc. of oil distillate in distillations 1
Allen, "Commercial Organic Analysis," 3rd Ed., Vol. 11, P t . 11, p . 2 2 9
.
T H E JOURiVAL O F I N D U S T R I A L A N D E N G I Y E E R I N G C H E M I S T R Y V o l .
37 0
of jooo grams of the “Residue.” T h e solids were detera n d analyzed with t h e results given below:
, mined
Fraction
Volume cc.
.
1. . . . . . . . . . . . . . . . . . 2.............. . . . . 3.............. . . . . 4.............. . . . . 5.............. .... 6. . . . . . . . . . . . . . . . . . I
..............
....
8. . . . . . . . . . . . . . . . . . 9. . . . . . . . . . . . . . .. , . 10.. . . . . . . . . . . . . . . 11.. . . . . . . . . . . . . . . , . 12.. . . . . . . . . . . . . . . . .
250 260 250 260 250 260 250 250 250 250 260 250
Wt. of solids in fractions None None None 1.2 5.8 11.0 15.2 14.4 12.1 5.4
None h-one
Per cent of anthracene in solids
... ...
... 58.20 47.26 46.83 40.52 43.76 39.19 21.73
...
I n the steam distillation, therefore, 0 . j I 7 per cent of anthracene was recovered from t h e “Residue” above zjo’, equivalent t o 0.383 per cent of t h e original tar. There was clearly less decomposition when steam was used, since t h e pitch contained b u t 5.6 per cent of free carbon, whereas t h a t from t h e dry distillation averaged j 7 per cent. Practically all of the anthracene comes over under 360’ in t h e dry distillation, a n d a t t h a t temperature little cracking has taken place, the pitch containing b u t 6.0 per cent free carbon. Above 360’ a n orange-colored, viscous, semi-solid material appears in t h e distillate a n d seems t o be indicative of marked decomposition. Fairly pure anthracene was prepared from t h e expressed solids by washing with gasoline, a n d subliming t h e residue. This anthracene melted a t 207’--211~ C. a n d when mixed with a sample of Kahlbaum’s anthracene, t h e mixture melted a t 2 0 8 ‘-2 I I ’. As a further test of t h e quality of t h e solids pressed from t h e high boiling distillates of water gas t a r , 50 grams of these solids recovered from t h e distillate between 289’ a n d 361’ were oxidized with bichromate a n d sulfuric acid. T h e anthraquinone after purification was sublimed giving 18.2 grams of crystalline anthraquinone. Anthraquinone prepared in this way was converted into t h e sodium anthraquinone-monosulfonate which in t u r n was converted into alizarine. A beautiful orange-red crystalline preparation of alizarine was obtained on subliming t h e product. Under laboratory conditions t h e transformation of anthraquinone into alizarine is difficult, a n d t h e yields obtained correspondingly low. From about 2 0 grams of anthraquinone only about 7 grams of alizarine were obt ained. SUMMARY
A systematic fractional distillation of water gas t a r shows t h a t it possesses a general resemblance t o coal t a r in its hydrocarbon content although, of course, t h e bases, phenols, a n d free carbon of t h e latter are absent or nearly so. T h e small amounts of material in the distillates resisting t h e action of sulfuric acid indicate a n absence of paraffin a n d naphthene hydrocarbons, a n d t h e marked variation in t h e capacity for halogen addition points t o variable amounts of unsaturated linkings outside t h e benzene ring. Benzene, toluene, the xylenes, mesitylene, n a p h t h a lene, a n d anthracene were shown t o be present in sub-
6,NO.5
stantial amounts. The preparation of the pure hydrocarbons a n d of commercial products could be effected by methods similar t o those employed with coal tar, a n d without encountering special difficulties. It would appear probable t h a t water gas t a r may offer a commercial source of supply for the various grades of benzol a n d solvent naphtha. Naphthalene could readily be produced, b u t there is no adequate demand, a n d it is likely t h a t t h e present trade conditions would not warrant t h e production of anthracene. SHEFFIELD CEIEXICAL LABORATORY YALEUXIVERSITY h7Ew HAVEN.CONN.
THE RADIOACTIVITY OF SOME TYPE SOILS OF THE UNITED STATES B y RICEIARD E. MOORE
Received March 6, 1914
Struttl first called attention t o t h e radioactivity of igneous a n d sedimentary rocks. T h e average of his results on igneous rocks showed a radium content of The 3.3 X 1 0 - l ~grams of radium per gram of rock. radium content of the sedimentaries was somewhat less. Jolyz has examined a large number of rocks for radium a n d thorium. His radium values are somewhat larger t h a n those of S t r u t t a n d other workers. T h e average of a number of his thorium determinations indicates t h e presence of I.58 X IO-^ grams of thorium per gram of rock. F l e t ~ h e r ,working ~ primarily with secondary rocks, has confirmed Joly’s results a n d a t t h e same time pointed out t h a t , with t h e exception of t h e calcareous rocks, those of t h e same types have always very nearly the same radium content. Although a considerable amount of work has been done on t h e radioactivity of rocks a n d minerals, very little has been a t t e m p t e d along this line with soils. A knowledge t h a t t h e atmosphere was radioactive was naturally followed by a n investigation of t h e activity of t h e underground air. Elster a n d Geitel, Bumstead, Blanc, Gadourian, Wilson, Ebert, Eve, Sanders, Satterly a n d others have contributed t o our knowledge of this subject. Whereas a study of t h e underground air indicates very plainly t h a t t h e soil is radioactive, i t does not give a n y ‘absolute values for the activity of t h e soil itself, as t h e activity of t h e underground air depends as much upon t h e emanating power of t h e radioactive matter in t h e soil as i t does upon t h e a m o u n t of t h a t material actually present. Some rough minimum determinations have been attempted. Wilson states t h a t there is probably seven times as much thorium as uranium in the surface soils a t Manchester. Blanc, on t h e other hand, estimates t h a t from 5 per cent t o 7 0 per cent of t h e activity of the R o m a n soil is due to thorium; while Sanderson’s4 work indicates t h a t I cc. of soil a t New Haven produces radium emanation in equilibrium with 8.9 X 1 0 - l ~ grams of radium, a n d thorium emanation in equilibrium with 1.3j X 1o-O grams of thorium. Fletcher5 gives the radium content 1 2
8
4 6
Proc. Roy. SOL.,( A ) 77 (1906), 472. Phil. M a g . , 17 (19091, 760; 18 (1909). 140; 23 (1912). 201. I b i d . , a3 (1912), 279. A m . Jour. Sci.. 32 (1911), 169. Phil. M a g . , 23 (1912). 279.
