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T H E JOURNAL OF INDUSTRIAL A N D ENGINEERING CHEMISTRY
Three parallel series were t h e n run with waters containing CaCL, MgClz a n d NazC03, respectively. T h e concentrations again ranged from o t o 1000 parts per million with differences of IOO p a r t s per million between samples. T h e results from t h e CaC12 series were t h e same a s in previous experiments. T h e results from t h e MgClz series were very similar, although t h e differences were not so marked. T h e beans were harder a s t h e concentration of t h e MgClz increased, a n d t h e samples could easily be placed in their proper order b y one who did not know t h e quantities of MgClz used. T h e Na2C03 in t h e water was found t o have a softening action. This fact is quite commonly known. No information, however, could be found concerning t h e concentration which might be advantageously used. T h e results showed a gradation in softness from the sample processed with distilled water t o t h a t processed with water containing 1000 p a r t s per million N a 2 C 0 3 . T h e former appeared t o have received t h e proper amount of cooking, while t h e latter appeared t o be greatly overcooked. The time of cooking these samples might have been adjusted so t h a t t h e product in each case would have been “fancy.” As t h e concentration of Na2C03 increased it was also observed t h a t t h e beans were darker in color. The use of Na2CO8 undoubtedly has some advantages, b u t this subject needs further investigation. In order t h a t a careful comparison could be made between effects of substances commonly found in waters, parallel series were r u n simultaneously, using waters containing CaC12, CaS04, Ca(HC03)2, MgC12, M g S 0 4 , Mg(HC03)2, XaZCOn a n d NaHC03. T h e waters were made up with concentrations of 0 , 50, 100, 200, 300, 500 parts per million expressed as CaC03. T h e results indicate t h a t t h e magnesium a n d calcium salts, when t h e y are present in a n y of the forms above mentioned, have a hardening effect on t h e beans; t h a t is, no difference could be detected in beans processed with water containing equivalent concentrations of calcium or magnesium whether a chloride, sulfate or bicarbonate. With bicarbonates of calcium or magnesium t h e gradation in hardness was not so marked a n d consistent as with t h e chlorides o r sulfates. This m a y be due t o t h e fact t h a t calcium bicarbonate a n d magnesium bicarbonate solutions are unstable, causing t h e Concentration t o change during t h e soaking a n d heating. N o difference could be detected between t h e beans canned with water containing magnesium salts a n d those canned with water containing calcium salts, when t h e quantities of t h e salts in solution were equivalent. It would seem, therefore, t h a t t h e effects of t h e magnesium ion a n d of t h e calcium ion are identical. T h e beans canned with t h e water containing S a 2 C 0 3 a n d those canned in water containing NaHC03 were compared a n d practically n o difference could be detected. T h e same softening effect was observed in t h e cases when water containing N a H C 0 3 was used as when N a 2 C 0 3was used. T h e authors expect t o continue this work. Experi-
Vol. 7 , No. 6
ments will be made with various kinds of beans a n d other soaked vegetables as well as fresh vegetables, fruits a n d berries. ’
STATE WATER SURVEY, UNIVEIISXTYO F ILLINOIS URBANA
THE USE OF COPPER SULFATE IN THE PURIFICATION OF SWIMMING POOLS BY
STANLEY JUDSON T H O M A S
Received December 24, 1914
Within t h e past two or three years, numerous articles have been written relating t o t h e sanitary conditions of indoor swimming pools. Studies have been made by Dr. William J. Lyster a t t h e University of Pennsylvania, Dr. M. P. Ravenel of t h e University of Wisconsin, a n d by various other workers throughout our eastern colleges a n d universities. One fact is emphasized by all these authorities-that t h e danger of transmission of zymotic disease through t h e swimming pool is real. It is easy t o see how a person suffering with walking typhoid may infect t h e limited amount of water in t h e pool a n d t h u s transfer t h e disease t o many bathers, who consciously or unconsciously t a k e the water into their mouths. This is b u t a n example. We might carry i t further a n d show how readily diphtheria, cholera, skin diseases, colds, a n d in fact almost a n y of our bacterial diseases may be contracted through this medium. It is not my intention t o go into t h e subject of t h e general care a n d upkeep of a pool. The Americait Physical Education Review of December, 1912, a n d February, 1913, has several excellent articles in this connection. The fact is indisputable t h a t , besides such general precautions as preliminary bathing with soap, inspection of t h e bather, a n d rejection of dirty bathing suits, etc., some chemical treatment of t h e water is necessary t o safeguard t h e health of t h e bathers. What this chemical shall be is t h e question I shall a t t e m p t t o answer. Excellent articles have been written by Dr. Ravene1,l Mr. S. C. Markley2 a n d others, recommending hypochlorite of lime as t h e disinfectant. As a precautiona r y t r e a t m e n t of public water supplies, there is no doubt t h a t this chemical is without a peer. Innumerable examples could be given t o show its efficacy. B u t i t must be borne in mind t h a t in t h e treatment of a public water supply more t h a n 2 parts per million of “hypochlorite” is seldom necessary. This means about 0.6 p a r t per million of available chlorine. When this maximum amount is used aeration of t h e water is necessary t o remove t h e disagreeable odor a n d taste of t h e “hypochlorite.” Now consider t h e use of this chemical in a swimming pool. Dr. Ravenel found t h a t I p a r t per million of available chlorine was necessary t o sterilize t h e water. T h a t means 3 parts per million of t h e hypochlorite, a n d as the usual method proposed is t o dissolve t h e salt in t h e pool directly one can imagine the unpleasant odor a n d taste of t h e water. “Aeration” is effected, i t is true, but “aera1
Dr. M. P. Ravenel, “The Hygiene of Swimming Pools,” Proceedings
of the Szxth Congress of the Amerzcan School Hygzene Association. 2 S. C. Markley, “The Use of Chloride of Lime in the Purification of Swimming Pools.” Amerrcan Physical Education Review, VIII, 2.
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T H E J O C R , V A L O F I N D U S T R I A L A N D E N G I N E E R I N G CH E M I S T R Y
tion” only releases t h e odor from t h e water i n t o t h e enclosed room surrounding t h e pool. T h e use of 2 . 5 parts per million “hypochlorite” was tried in t h e Taylor Gymnasium pool, at Lehigh University, a n d even at this dilution t h e odor was marked. T h a t t h e t r e a t m e n t was not effective is shown b y t h e results of t h e bacteriological analyses of t h e pool during t h e t r e a t m e n t (Table I) : TABLE I-B.4CTERIOI
.OGICAL
GYMNASIUM SWIMEXAMINATION cIF TAYLOR MINO P O O L
Day and Time Count per cc. Gelatin Apar Kovember, 1914 50 10 8 12.00M. 9 9.00a.~. 200 1400 10 10.30a.w. 2700 1500 10 11.15A.M 3000 5300 10
2.ooP.M.
10 11 12 13 13
5 . 4 5 P.M. 3.00p.m. 5.00P.M. 2.30P.M. 2.45P.M.
14
5 0oP.M.
2
5
800 50 400 1000 800 3000 100 500 0 3
50
400
B . coli REMARKS per cc. 0 Fresh water. 3 men had been in the pool. 0 50 40 men in pool since last 200 samnle. 2.5-p-k.-m. hypochlorite ad0 ded a t 11.30 A.M. No one in pool since 11.15. 0 340 400 3000 gal. fresh water added. 100 0 Sample taken after 2.5 p. p. m. hypochlorite were added. 10
F r b m these results i t m a y be seen t h a t , though 2 . 5 p a r t s per million of hypochlorite of lime purifies t h e water shortly after i t s introduction into t h e pool, i t soon loses i t s germicidal properties a n d is unable t o destroy t h e bacteria which are constantly being brought in b y new bathers. T o a d d 2 . 5 p a r t s per million of t h e “hypochlorite” every d a y would probably solve t h e problem from a bacteriological standpoint, b u t t h e odor would be t o o offensive for this form of t r e a t m e n t t o be considered. This pool is equipped with a double unit mechanical filter in which alum is used as a coagulant. By this refiltration system t h e water is always k e p t clear. T h e bacterial content of t h e pool cannot be kept low, however, b y this t r e a t m e n t alone. T h e idea was conceived, a n d acted upon, of using a small a m o u n t of copper sulfate in connection with t h e alum t r e a t m e n t , n o t , however, b y mixing t h e copper sulfate with t h e alum, b u t b y introducing i t directly into t h e pool after t h e completion of t h e a l u m coagulation, which removes t h e carbonates a n d bicarbonates t h a t would otherwise hinder t h e action of t h e copper sulfate. T h e result of using 0.4 p a r t per million of copper sulfate proved t o be very satisfactory, as will be shown later. I shall now discuss t h e use of copper sulfate as a germicide a n d a t t e m p t t o show i t s advantage over hypochlorite of lime as a disinfectant of swimming pools. I n a paper written in t h e early So’s, Carl von Naegeli,l one of t h e greatest German botanists of t h e p a s t century, showed how exceedingly sensitive certain living plants are t o minute quantities of various metals. H e found t h a t certain Spirogyra are unable t o resist t h e toxic effect of one p a r t of copper to one thousand million p a r t s of water, a n d t h a t minute quantities of other metals, such as silver, lead, tin, iron a n d mercury, manifested “oligodynamic”* properties. Israel a n d 1 “Ueber oligodynamische Erschemungen in lebenden Zellen,” von Naegeli 2 “Oligodynamic”-derived from two Greek words meaning the force within a small quantity of a substance.
497
Klingmann,l i n 1897, studied t h e effect of copper on certain bacteria, Spirogyra a n d animal forms. Bacteria a n d Spirogyra were very sensitive a n d were easily killed with dilute solutions. I n t h e case of t h e animal forms, while t h e toxic effects were visible in most cases with dilute solutions, Vorticella a n d a few others required a larger a m o u n t of t h e metal. Locke found t h a t traces of copper contained in water distilled in copper vessels were sufficient t o destroy Tubifex (one of t h e annelid worms) a n d tadpoles. Cushing,2 i n 1899, gave a good description of t h e work done u p t o t h a t time along this line. T h e fact t h a t these discoveries were of great economic importance was first brought o u t b y Dr. George T. Moore of t h e U. S. Department of Agriculture. I n 1904 t h e U. S. Department of Agriculture, Bureau of P l a n t I n d u s t r y , published3 t h e results of D r . Moore’s experiments with copper sulfate as a n algicide a n d disinfectant in polluted water. I n t h a t paper i t was recommended t h a t copper sulfate be used in t h e dilution of one p a r t t o one thousand p a r t s of water. I n December of t h e same year, T h e A m e r i c a % J o u r n a l of P h a r m a c y published a n article b y Dr. hloore4 a n d one b y D r . H e n r y Kraemer; of t h e Philadelphia College of P h a r m a c y , I n his paper, Dr. Moore reviewed thoroughly t h e practical application of copper sulfate in municipal water supplies, chiefly as a n algicide. T h e first reservoir so treated was t h a t of t h e Winchester Water Co. at Winchester, K y . T h e success of t h e t r e a t m e n t is best given in D r . Moore’s own words: “ I n June, 1903, our attention was called t o t h e condition of t h e reservoir a t Winchester, K y . This supply was constructed in 1890, a n d after t h e first three years a strong odor a n d taste were noticeable in t h e water during t h e hot summer months. This condition gradually increased until t h e water attained such a degree of offensiveness a s t o make i t s use for a n y purpose almost intolerable. Aeration a n d mechanical filtration were tried without effect, a n d i t seemed t h a t t h e only hope for relief was t o abandon t h e entire, reservoir a n d go t e n miles t o t h e Kentucky River for t h e source of a new supply. T h e cost, however, was too great t o be considered, a n d for this reason t h e difficulty was considerably increased. 4 microscopical examinaton of t h e water showed t h a t t h e odor a n d taste were d u e t o t h e presence of one of t h e blue-green algae, a n d i t was believed t h a t t h e application of copper sulfate a t t h e r a t e of about I t o 5,000,000 would be sufficient t o destroy these forms; consequently, there being n o objection on t h e p a r t of either t h e water board or t h e health authorities, a t r e a t m e n t was made, a n d t h e results have been everything t h a t could be desired. Within three or four d a y s t h e odor disap1 Israel and Klingmann. “Oligodynamische Erschemungen (v. Naegeli) an pflanzlichen und thiereschen Zellen,” Virchow’s Archiv , 1897, pp 293-340. 2 Cushing, “Pharmacology and Therapeutics.” 1899, p. 159. 3 “A Method of Destroying or Preventing the Growth of Algae and Certain Pathogenic Bacteria in Water Supplies,” by Moore and Kellerman, U. S. Department of Agriculture, Bureau of Plant Industry, Bull 64. 4 “A New Method for the Purification of Water Supplies,” b y Dr. George T. Moore (an a‘ddress given before the American Philosophical Society, Oct. 21, 1904), American Journal of Pharmacy, 76 (1904). 553. 5 “The Copper Treatment of Water,” b y Prof. Henry Kraemer. American Journal of Pharmacy, 76 (1904). 574
’
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERIn’G C H E M I S T R Y
49 8
*
peared a n d t h e water was perfectly clear. This summer a t a b o u t t h e same time i t was feared t h a t t h e algal growth was reappearing, a n d for this reason another slight t r e a t m e n t was made, b u t with this exception n o copper has been added t o t h e water since t h e original t r e a t m e n t in June, 1903, a n d it has remained perfectly clean a n d sweet.” After citing numerous other examples of t h e efficiency of copper sulfate as a n algicide Dr. Moore says: “Very naturally a f t e r i t was noted t h a t t h e algae were so susceptible t o infinitesimal quantities of copper, i t seemed worth while t o test t h e effect of this metal upon typhoid a n d cholera germs, these being t h e t w o pathogenic forms which are most commonly conveyed b y water. As t h e result of some 500 or 600 experiments, i t was demonstrated t h a t , while these bacteria were not as sensitive as t h e algae, still t h e dilution necessary t o produce death was sufficiently great t o warrant t h e belief t h a t under certain conditions efficient sterilization of large bodies of water could be brought about.” Dr. Kraemer, i n corroborating Dr. Moore’s results, goes further into t h e effect of copper sulfate on t h e h u m a n system. He points out t h a t t h e salt was most beneficial i n removing algae from watercress beds, while not harming t h e cress, a n d adds: “It seems t o m e t h a t this is in a measure d u e t o t h e fact t h a t i n t h e algae t h e entire individual is comprised in a single cell, which performs all t h e vegetable as well as t h e reproductive functions, a n d being entirely surrounded b y t h e water containing t h e copper sulfate, all t h e life processes of t h e plant are affected, there being no way for i t t o distribute t h e solution t o other cells, a n d t h u s b y a dilution minimize t h e toxic action of t h e copper.” D r . Kraemer allowed copper foil t o dissolve i n water in conducting his experiments. While this has t h e toxic power of t h e sulfate it h a s n o t its added power of sedimentation. H i s results are conclusive i n showing t h a t t h e intestinal bacteria like colon a n d typhoid are completely destroyed b y placing clean copper foil in t h e water containing t h e m . Mr. Alfred M. Quick,] in 1904, gave t h e results of t h e use of copper sulfate in Lake Clifton of t h e Baltimore Water works. On July 28, B . coli were present in I cc. of t h e water. T h e next d a y copper sulfate in t h e dilution of I : 6,390,000 was used. On August grd, analysis showed B. coli absent. James A I . Caird2 showed t h e results of t h e use of 1 l / 2 p a r t s per million of copper sulfate in t h e water supply of Elmira, N . Y . On June 24th, analysis showed B c o l i 2 per cc. a n d t h e total count was 315 per cc. On June 30th, after treatment, B . coli were absent a n d t h e total count was I S per cc. I n April, 1905, in a Bulletin3 of t h e U. S. Department of Agriculture, Moore a n d Kellerman supplemented D r . Moore’s previous article a n d gave a complete description of all phases of t h e question. Numerous 1
’The Use of Copper Sulfate in Lake Clifton,” b y A M . Quick, Engi.
neering News. 62. 284. 2
“Purification of the Water Supply a t Elmira, N . Y.,”b y J. M. Caird,
Engineering News, 52, 34. 8 “Copper a s an Algicide and Disinfectant in Water Supplies,” by Moore and Kellerman, U. S. Department of Agriculture, Bureau of Plant Industry, Bull. 76.
Vol. 7 , NO. 6
reports from cities upon t h e effect of t h e t r e a t m e n t are given. Notable among these is one from Columbus, Ohio. A badly polluted water supply h a d caused for over a year a n almost continuous epidemic of typhoid fever. T h e copper sulfate t r e a t m e n t was resorted t o b u t later discontinued “after t h e daily papers published glaring accounts of t h e dangers a t t e n d a n t upon such treatment.” A tabulation of t h e d a t a shows clearly t h e results of t h e use a n d non-use of copper sulfate. T h e salt was used in t h e dilution of I p a r t in I , joo,ooo. Month June July
Typhoid cases reported 24 33 52 16 16 8
No copper used.. . . . . . . . . . . . . . . . No copper used.. Copper used after 1 9 t h . . . . . Copper used . . . . . . . . . . September . . . . . . . . . . October Copper used Copper used. . . . . . . . . . . . . . . . . . . . November Copper used. . . . . . . . . . . . . . . . 4(a) Copper discontinued after 5th 91 No copper used.. . . . . . . . . . . . . . . . February 376 No copper used.. . . . . . . . . . . . . . . . T o March 27th 279 ( a ) 17 cases were reported, b u t only 4 were users of city water.
...............
T h e chief objections t o t h e use of copper sulfate were based on t h e fact t h a t i t might be harmful t o m a n . Aside f r o m t h e puerile charges against i t t h a t have been made b y certain ignorant advertisers a few doctors maintained t h a t nothing was known of t h e effect of continued use of t h e salt. It would be impossible even t o refer t o most of t h e literature t h a t has been published relating t o t h e harmlessness of this t r e a t m e n t . Dr. Moore a n d D r . Kraemer have both colIected statements from t h e leading toxicologists i n this a n d m a n y foreign countries which answer fully all objections. Dr. Henry Kraemer published a n article’ in 1905, showing t h e amounts of metallic copper normally contained in over a hundred foods. If these foods can be eaten with impunity, i t m a y be easily seen w h a t slight chance there is of being poisoned b y t h e small a m o u n t of copper we use for water purification. D r . Kraemer’s results, Table 11, show t h e quantities of copper i n milligrams found in a kilogram of t h e foods, which corresponds t o p a r t s per million in a tabulation of t h e results obtained in its use in water. As metallic copper comprises only 2 5 per cent of copper sulfate these results must be quadrupled if a n exact comparison is t o be made. TABLE11-QVAXTITY
METALLICCOPPER I N MILLIGRAMS P E R KILOVARIOUSFOODS 36.8 Egg, yolk (11) 5.6 Milk. cow (12) 1.6 1 . 0 Egg, white (11) 7 . 2 Oatmeal (19) 4.27 2 . 3 Figs(l5) 15.1 Peas, French (7) 59.4 Grapes, CatawPotatoes (5) 2.8 47.0 ba (19) 1.01 Strawberries (15) 8.0 4 5 . 0 Kidney, beef (12) 4 . 0 OF
GRAM OF
Almonds (15) Apricots (15) Cherries (15) Cocoa, pure, n o husk (18) Cucumbers (15)
Add t o this t h e statements of m a n y eminent physicians2 relating t o t h e beneficial effects of copper as a curative measure for typhoid fever a n d cholera, a n d t h e exhaustive s t u d y made b y D r . Walker3 of London, a n d our case seems t o be complete. Dr. Burg of Paris visited or corresponded with eyery i m p o r t a n t copper mine a n d foundry in Europe where workmen could possibly become impregnated with copper. T h e results of his s t u d y lead t o t h e following conclusions 1 Henry Kraemer, Ph.D., “The Use of Copper in Destroying Typhoid Organisms and the Effects of Copper on Man,” American Journal of Pharmacy. 77, 6. 2 Dr. Lucien F. Salomon, N e w Orleans M e d i c a l and Surgical Journal, June, 1902. 3 Dr. A. deN. Walker, “The Prophylactic Power of Copper in Epidemic Cholera,” London, 1883.
June,
T H E J O C R N A L O F I N D U S T R I A L A N D EATGINEERIil‘G C H E M I S T R Y
191j
which he addressed t o t h e Academy of Medicine a n d Sciences. “I-Complete i m m u n i t y from cholera of t h e immense majority of all workmen whose calling necessit a t e s their being habitually in contact with copper dust. “a-Copper a n d its alloys, brass a n d bronze, permanently applied t o large surfaces of t h e common integument, are a most precious preventative, which ought in no mise t o be neglected a n d can cause no inconvenience. If these means leave something t o be desired as a prophylactic, it will probably be found expedient t o reduce t h e metal t o a n impalpable powder a n d t o ingest a few pinches. ‘:3-111 t h e t r e a t m e n t of cholera, copper, opportunely administered, whether in copper filing alone or in a n y other form which experience shall determine, affords t h e greatest probability of proving in t h e hands of t h e physician a powerful means of cure.” Having been convinced t h a t even in fairly large doses copper sulfate is harmless t o t h e h u m a n system, I tried its germicidal effect in t h e Taylor Gymnasium pool. Xs. t h e pool water a t t h e time was being refiltered daily, a small amount of alum being added t o aid t h e mechanical filter-I took t h e opportunity of first determining t h e efficiency of t h e alum t r e a t ment. A s t h e copper t r e a t m e n t immediately followed t h e alum t r e a t m e n t , I have tabulated m y results together. Table I11 shows t h e results of t h e use of alum a n d of alum a n d copper sulfate.
499
S L-1111.4 R Y
The advantages of copper sulfate over hypochlorite of lime as a disinfectant for swimming pools therefore may be summarized as follows: I-It is more effective because i t does not undergo chemical change readily. Hypochlorite owes its power t o t h e chemical change a n d is afterwards useless. 11-It is not irritating t o t h e eyes a n d mucous membranes as is iihypochlorite” if t h e latter is used in germicidal quantities. 111-It is cheaper. IT‘-It has no odor. If all other conditions were equal this last fact alone would prove its great advantage over “hypochlorite.” DEPARTMENT O F BIOLOGY,LEHICHUNIVERSITY SOUTH BETHLEHEM, PA
THE VALUATION OF COMMERCIAL ARSENATE OF LEAD By R. H. ROBINSON AND H. V. TARTAR Received January 16, 1915
T h e practical value of t h e arsenates of lead as insecticides depends upon their arsenic content a n d their comparative insolubility in water which prevents t h e m from being injurious t o foliage. There are three arsenates known: t h e lead of hydrogen or “ a c i d ” arsenate, t h e basic or “ n e u t r a l ” arsenate, a n d t h e pyroarsenate. T h e latter salt is unimportant from a spray standpoint, since it is probably not present in t h e commepcial brands upon t h e market, due t o t h e fact t h a t t h e pyro salt cannot exist in t h e presence of water a n d , t h u s far, has been prepared only b y heating t h e pure hydrogen arsenate a t high temperatures as shown by T a r t a r a n d Robinson.’ Previous investigaT s a i E 111-BACTERIOLOGICALEXAMINATION O F TAYLOR GYMNASICM tions by T a r t a r a n d Robinson’ have shown t h a t pure SWIMXING P O O L Gelatin B. coli Gelatin B . coli lead hydrogen arsenate can be prepared corresponding Date count per Date count per 1914 per cc. cc. ADDITIONS 1914 per cc. cc. ADDITIONS in composition t o t h e theoretical formula PbHAs04, 5/20 8,000 1 , 0 0 0 ) 5/11 4 0 giving upon analysis 32.98 per cent arsenic oxide a n d 21 6 , 0 0 0 50 1.0 p. p. m. 11 790 7 22 18,000 100) alum per day 63.92 per cent lead oxide. The basic arsenate was 1 2 9 , 0 0 0 180) 23 30,000 150 13 18,000 100 24 9,000 80 also found t o be of constant composition when pre25 27,000 300 14 48,000 90 ’.’ P . P. m. 1 5 16,500 2 5 0 per 26 5,000 pared from pure salts a n d gave upon analysis 23.42 2i 2,500 ;) 16 6,900 400 28 100 0 0.04 p. p , m. 1 i 36,000 400’ per cent arsenic oxide a n d 7 4 . 7 2 per cent lead oxide. 29 2 , 0 0 0 c u , ~ y ~ ~per a Practically, t h e n , there are two kinds of lead ar18 4,800 20 22,000 gallons 30 500 9 fresh water 6/ 2 5 , 0 0 0 senates: ( I ) the hydrogen, a n d ( 2 ) t h e basic arsenate 19 10,000 200 3 6,000 14 generally used as a spray material; manufacturers of Gelatin count B. coli AVERAGE P E R \TrEEK per cc. per cc. commercial brands usually produce one or t h e other 1st Alum t r e a t m e n t . , . . . . . . . , . . . . . , . . . . 35,000 390 form a n d label t h e m as such. T h e hydrogen arsenate 2nd 2.5 p. p. m. “hydrochlorite”. . . . . . . . . . 1,500 148 3rd 0.4 p . p. m. CuSOa.. . . , . . , . , . , , , . . . . 3,014 5 is found on t h e market under t h e trades name “ a c i d ” Although copper sulfate is slightly more expensive or “dibasic” arsenate of lead a n d t h e basic is commonly t h a n hypochlorite of lime, a b o u t $1.00 per hundred- known a s t h e “ n e u t r a l , ” “triplumbic” or ‘ I tribasic” weight, i t is effective in much smaller quantities a n d arsenate of lead. There are, however, many brands t h a t do not specify either a hydrogen or a basic sample hence is cheaper t o use. T h e germicidal action of t h e copper sulfate is proba- b u t are simply labeled “arsenate of lead.” I n t h e analysis of t h e commercial brands of lead bly t h a t of a crystalloid, permeating t h e cell wall arsenates, t h e specific determinations usually required, a n d thereby producing t h e toxic effects. as evidence t h a t t h e product is not a violation of t h e I n t h e presence of t h e bicarbonate of magnesium a n d Federal Insecticide Law, consist of a n estimation of calcium t h e following reaction takes place : t o t a l arsenic oxide, total lead oxide, water-soluble CuS04 C a ( H C O y ) r = CaSOa C U ( O H ) ~ 2C02 arsenic oxide, a n d moisture. This is sufficient t o This chemical change, while it destroys t h e toxic ascertain whether t h e sample fulfills t h e requirements power of t h e salt, really aids in t h e ultimate purifica- a s demanded b y law, b u t it does not give evidence of tion of t h e water since t h e hydroxide formed acts a s a t h e exact nature of t h e sample. coagulant uniting with t h e suspended organic matter. 1 Tartar and Robinson, J . A . C. S., 36 (1914). 1843.
I
+
+
+
