LUlJAIV, I'l:!IlERlES RfSEARCH 8OoIRIOFCAMDA.
MERCUR\r AND THE CONTAMINATION OF FRESHWATER FISH
E.G. Bligh
Winnipeg 19, Manitoba
DATED April 1970
This series includes unpublished preliminary reparts and data recardsnat intended for general distribution. They should not be referred to in publications without clearance from the issuing Baard establishment and without clear indication of their manuscript ,totUI.
MERCURY AND THE CONTAMINATION OF FRESHWATER FISH
byE.G.BlIgh
Fisheries Research Board of Canada Freshwater Institute Winnipeg 19. Manitoba
Mercury is widespread iIl; nature and it has been estimated that the earth's crust contains 0.4 ppm. It occurs principally as the sulphide "cinnabar" which Is mined and roasted to yield metallic mercury. Mercury production in Canada is limited to Cornineo's mine at Pinch! Lake, B.C .. which resumed operations in
1968. having been closed since 1945, and produces about 1400 lb. mercury per day.
SlIverqulck Development Co. Ltd. Is scheduled to produce about 1000 lb. mercury per day starting In 1970 from an open pit mine near Goldbrldge. B.C. Spain and
Italy produce about 40"/0 of the world's supply of mercury with the U.S.S.R. and the
U.S.runningin3rdand4thplace, respectively.
The U.S. appears to be the world's iargest consumer of mercury; the recorded figure for 1968 was 5.7 million pounds. Canadian consumption in 1969 was 300.000 lb. of which about 200,000 lb. was used by the chlor-alkali Industry. A breakdown of our consumption in 1967 and the principal uses of mercury in the U.S. are recorded
Mercury has been used for ages in the recovery of gold and silver from ores
but its use in this capacity is noW relatively minor. World consumption of mercury
has Increased markedly since World War II through expansion of the chlor-alkali Industry and Increased use in the electrical industry.
Inasmuch as the chlor-alkal! industry Is by far the most important user of
mercury In North America, a brief description of how mercury Is used and lost in a
typical plant may be pertinent.
The chemical equation for the process Is as follows:- /:;::~ , "C> • c' T ·C',1
(2 Hg) + 2 NaOH + H2t
A flow sheer of a typical chlor-alkaliplantoperation is shown i nFigure\.
values at various points in the process r~present possible losses of mercury in grams
per ton of chlorine produced. In the Primary Cell, parallel streams of saturated
sodium chloride and mercury are electrolyzed; sodium is amalgamated at the
mercury cathode and chlorine is evolved at the graphite anode. In the Secondary
Cell, the sodium amalgam is reacted counter-current with water to give 50% sodium
hydroxide and hydrogen. The denuded mercury is pumped back to the Primary Cell
to complete the cycle.
On leaving the Primary Cell, the hot and weakened sodium chloride solution
is stripped of chlorine by vacuum and aeration. After saturation through the addition
of sodium chloride or by pumping it through an underground salt deposit, it is
treated with sodium carbonate and barium chloride to remove such impurities as
alkaline earth metals and sulphate. Just prior to returning to the cell, the brine is
filtered to remove graphite and the pH is adjusted.
Chlorine liberated in the Primary Cell and by vacuum dechlorination is cooled, dried with SUlphuric acid, and liquified. Chlorine removed by aeration is converted to hypochlorite by absorption in lime or caustic soda. The caustic soda leaving the denuder is partially cooled and may be filtered prior to immediate use or shipment. The hor hydrogen leaving the denuder Is saturated with mercury vapour
and must be cooled for recovery of mercury.
Some brief comments on the potential losses of mercury indicated in
Figure 1 are llsted below:
Chlorine system - very small mercury loss; return condensate
Brine system brine will contain 3-5 ppm mercury as
tetrachloro-complex which is precipitated
with sludge; no brlneor sludge should be
discharged with waste water.
Hydrogen system large mercury losses can occur; hydrogen must
be cooled to at least SoC preferably by in-
direct cooling to enable addition of con-
Alkali system contains metallic mercury; should be removed
by filtration and residues must not be dis-
charged with waste water.
may contain spilled mercury and residues;
mercury traps and removal of mercury as
sulphidearpH8inpresenceofironehioride
due to mercury vapours from faulty mercury
pumps and hydrogen leaks.
It has been estimated the chlor-alkali plants using mercury cathodes lose
anywhere from 0.25 to 0.5 lb. mercury per ton of chlorine produced. Plants with a
daily production in excess of 100 tons of chlorine are not uncommon and approximately
500;0 of the Canadian production of chlorine and sodium hydroxide is in plants using Noel
Various Condensate 1 wost~g~ater mercury cells (sec Table 11).
I would make brief mention that mercury compounds have been widely used in the pulp and paper industry as slimicides. Slimicides are used In wood~ preparation areas and in the vicinity of paper machines to control slime fungi which are a nuisance in mill operation. Organic mercury compounds like phenyl- mercuric acetate are extremely effective against these slimes. During the last
10 years, many countries including Canada have for the most part discontinued using these compounds owing to regulations preventing the use of mercury con ~ taining papers in the wrapping and packaging of foods. Only about half a dozen
Canadian mills were still using mercury slimicides in January 1970 and most of
Canadian consumption of mercury in seed dressings has decreased slightly in recent years and now totals about 25,000 lb. per year (Fimreite. 1969).
These compounds appear to be causing serious problems with birds like the pheasants in Alberta. but there is no evidence that they have affected fish. Lofroth(1969) indicates a further concern however, "The crop which is grown from seeds dressed with minimal Quantities of methylmercury contains amounts enough to cause an accumulation in the food chain reaching man both when the crop is consumed directly or via animal products."
To sum up the uses of mercury, it would seem most appropriate to take a very close look at chlor-alkali plants as sources of mercury pollution In Canada.
Fish and shellfish are noted for their ability to concentrate heavy metals and mercury is no exception. In fact they can tolerate mercury levels that are hazardous to human health if eaten. The Japanese problem at Minamata Bay in the 1950's is perhaps the best documented case where 111 casualties resulted from the consumption of fish and shellfish contaminated with mercury (Lofroth, 1969). Methyl mercury compounds were considered the toxic agents originating from a
chemical plant using mercuric oxide as a catalyst in the preparation of acetalde-
hyde. Waste from this plant contained up to 20 ppm mercury. There was a vinyl
chloride plant on the Oay, also, which used mercuric chloride as a catalyst.
After 2 years of treatment of the effluent for mercury removal, mercury levels
In shellfish dropped from 05 to 10 ppm (dry wt. basis).
A similar Incident occurred in Nligata, Japan, in 1965 where 26 cases of
poisoning resulted in 5 deaths from the daily consumption of fish containing
approximately 5 ppm mercury. It may be of interest that the Japanese are the world's heaviest consumers of fish (62 lb./capita/annum vs Canada's 13 lb.).
Sweden has experienced problems with mercury in freshwater fish more recently. They established that the mercury originated from the widespread use of mercury slimicides in pUlp mills and the use of mercury cathodes in chlorine plants. Although they have recorded levels in pike as high as 9.8 ppm, and the
Swedes are also heavy fish eaters (45 lb.!ca·plta/annum), there were no reported cases of mercury poisoning in humans. However, they have closed many areas
(0 fishing. Much good research has been done in Sweden on mercury in the environ- ment. Mercury slimicides have been banned, chlor-alkali plants have been (orced to treat or retain effluents, and the use of methyl mercurials in agriculture has been stopped to prevent further declines in many bird populations.
When mercury is discharged into a river or lake neither organic nor inorganic mercury are taken up appreciably by aquatic plants but there can be considerable surface adsorption on submerged plants (Hannerz, 1968). Adsorption on particulate matter and in sediments is extensive and much of the mercury is immobilized in this way. However, Jensen and Jernelov (1969) claim that all types of mercury are readily converted to methyl mercury compounds by sediment organisms and fish slime.
All mercury compounds are taken up by fish both directly from the water Accumulation can be very rapid but elimination Is slow. biological ha1flife of mercury in pike muscle has been reported at 70 days.
Highest mercury concentrations appear in the kidney and liver and lowest in muscle and bone. Methyl mercury compounds are absorbed most rapidly having concentration factors of 2000 and 9000 for pike muscle and kidney. respectively.
To further illustrate this point. fish from water in Sweden containing 0.13 ppb mercury had 400 ppb in their tissues representing a concentration factor of 3000.
Rucker and Amend (1969) reported that hatchery use of mercurials for disease treatment can lead to elevated mercury levels in the fish. Sockeye salmon treated for one hour per week with ethyl mercury phosphate for bacterial gill disease contained 8 ppm mercury after treatment for four months. Levels
fed for 30 days on fingerlings containing 3 ppm mercury had highest mercury levels in liver (30.5 ppm) and lowest in muscle (1.9 ppm).
Mercury levels in fish muscle vary greatly even within species. In wild fish. highest concentrations are found in larger or older fish. Therels some evidence that mercury in fish muscle is in the form of methyl mercury compounds which are highly toxic to humans.
Although mercury compounds are highly toxic to fish. I am aware of no reports of fish kills due to mercury pollution. Mercuric chloride is considered to be "infinitely" toxic to fish which means that even traces will be toxic if exposure continues long enough. For example it has been reported that 0.01 ppm mercuric chloride is toxic to minnows in 90 days. Dr. MacLeod at the Freshwater
Institute has found that phenylmercuric acetate is 10 times more toxic to rainbow trout than mercuric chloride and that the latter was twice as lethal at lS o e than
Mercury poisoning in humans has been known ever since the discovery of metallic mercury. Mercury vapours are extremely toxic and reliable sources claim that 1-2 mg of methyl mcrcury per day produce clinical signs of poisoning
In man. Such a dose would be equivalent to 200 g of fish per day with a mercury contcnt of 5-10 ppm.
The biological halfllfe of mercury In man has been reported at 70 days.
Studies have shown that the main route of excretion is via the feces rather than the urine and only minor quantities arc deposited in hair. Nevertheless, hair mercury levels of 60-530 ppm were recorded in Japan, 7.9 ppm In Sweden, and up to 20 (i"mes the normal level of 1.5 ppm were found in Finland.
The human fetus acquires higher concentrations than the mother-la-be which explains the cause of congenital cases of mercury poisoning born of mothers having no symptoms of methyl mercury poisoning.
Some of the symptoms of mercury poisoning in man are -
impaired hearing
slurred speech
impaired muscular co-ordination
hysteria
flaccid paralysis
coma followed by death.
------The Canadian Problem Recognition of the problem of mercury pollution in Canada occurred on November 27, 1969 when the Saskatchewan Government reported that fish taken from the Saskatchewan River contained abnormal amounts of mercury
(See Wobeser et aI., 1970). Knowing that this posed a threat ro human health and could also seriously jeopardize the entire Canadian freshwarer fishery.
the Federal Department of Fisheries and Forestry immediately placed all fish
from the Saskatchewan River System under detention. The Freshwater Institute
was at the same time asked to set up a laboratory for analyzing fish and to
investigate the problem. We immediately began to analyze fish on a dally basis
for the Inspection Service and only flshwithlessthanO.Sppm merc ury(wet
weight on muscle tissue) were released for sale. All other fish were incinerated
to ensure that they could not be eaten by humans, animals, or wildlife. Inas-
much as the Freshwater Fish Marketing Corporation is the sole buyer of fish from
the area, there was no problem to screen all fish coming from fishermen.
Once public health measures had been established, an investigation was
launched to determine the cause of the problem. As mentioned earlier, chlor-
alkali plants were suspect and our first srepwas to visit the chlor ineplantin
Saskatoon. In cooperation with the Saskatchewan Water Resources Commission we
discovered that the plant was discharging mercury into the Saskatchewan River.
I would add that the plant management had never been forbidden to discharge
mercury and on learning of the seriousness of the situation voluntaily agreed to
modify their process to prevent any loss of mercury to the river. Within 10 days
they had shut off their discharge and a lagoon was constructed to hold their wastes.
Knowing that Ontario had the greatest concentration of chlor-alkali
plants in Canada, the Ontario Water Resources Commission was alerted that these plants should start to eliminate any mercury losses to the environment. They immediatelylaunchedaprogramandallpulpmlllsandallchiorineplantshave now been formally advised that mercury must not be discharged into rivers and
In the meantime we needed to know what kinds of fish and what lakes had been contaminated. In co-operation with the Federal Fish Inspection Branch we found the following levels of mercury cOlltamination (See also Table III " V):
Saskatchewan River lC;;~!!'J>_e...!.!!!!LIi£!!!.0... Goldeye' Satisfactory Sturgeon Too high
Northern Pike Walleye Too high Sauger
Whitefish Satisfactory Cisco
All fish from the following lakes were satisfactory. ~~ ::.nn~~~~~:iS L. Manitoba DauphlnL. Moose L.
~~l£~_~.!..t.!..t.!..!"p_e...&...required a detailed survey and the Manitoba Government
assisted by obtaining samples from all parts of the lake. In general the Northern
basin was found to be less contaminated than the Narrows and Southern Basin.
Whitefish Cisco All satisfactory Sucker Burbot ~:~~:~h::~eh T~.O hi.~h Sauger. about 60% Northern Pike, about 30% " Walleye, about 20%
Fish from the Nelson River System will be analyzed as samples become
We now had another problem - where was mercury c::oming from in the
southe end of Lak.e Winnipeg. We have examined fish from the Red, Assiniboine,
and Winnipeg Rivers, and although more data is required, the Winnipeg River was
found to be the most contaminated (see Table VI). The chlorine plant at Dryden
has been visited and they have taken steps to eliminate any discharge of mercury
• Common names of fishes used in this manuscript are those prescribed by the American fisheries Society, 1960. Into waters of the Wabigoon River which eventually drain Into Lake Winnipeg.
The pUlp mills In the Kenora area, and the onc at Pine Falls, discontinued Ule of mercurial 11Imlcldel some years ago. In cooperation with the Government of
Ontario and Manitoba, we are doing a detailed study on mercury levels in fish in the affected waters between Dryden and Lake Winnipeg (see Table Vll).
Meanwhile we have the Great Lakes' situation to investigate (see
Table VIll). Also, in cooperation with the Fish Inspection Branch we are doing a national survey on the mercury content of Canadian fish, including both marine and freshwater species.
Before concluding I would summarize some of the other investigations that a.re going on within the Freshwater Institute.
~~..!..£E.!.I_~.!!!!..Y.~.! On initiating our investigations we had an immediate need for a reliable and rapid method for determining trace quantities of mercury in fish tissue. Although neutron activation is considered the most sensitive method available, it was far too slow and expensive. The standard dithizone extraction procedure has limited sensitivity and therefore requires large samples. Atomic absorption appeared the method of choice and after detailed experimentation the procedure outlined in Appendix I was perfected (Uthe, Armstrong and Stainton,
1970). It has now been semi-automated and is in great demand throughout Canada and the U.S. Check sample resulll in Table IX indicate that this method compared very favourably with those used elsewhere.
~.1.!'.Y.!_~~~~ Japanese and Swedish scientists have repolled that mercury in fish muscle occurs in the methylated form but techniques for determining methyl mercury compounds require refinement and work is proceeding in this direction. Furthermore, Jensen (1969) has Indicated that methyl mercury may not be the dominant form of mercury In fish muscle. It Is Important that the form
of mercury In tissue be known to the toxicologist and In order that means of
removing It through processing might be developed. Although there Is no slgnlfl-
cant loss of mercury on cooking of fish, a 20% reduction In mercury content was
obtained on flame drying of minced whole pike. Further trials will be conducted
as well as feeding tests on meals containing mercury residues.
~!!Y~oJ.2.B..!E.!!._~~~.!~!.. Aquarium studies are in progress to determine
the effect of water temperature on the toxicity, accumulation and elimination of
mercuric chloride and phenyl mercuric acetate in rainbow trout. The sublethal
effects of mercurials on fish behaviour and reproduction are also being investigated.
It is expected that these studies will provide needed information for the establlsh-
ment of tolerances for mercury in water to ensure healthy fish that are safe (or
human consumption.
~e..!.£.!1'!"y_!....n_~~ji!!1_e..!1.1.! Swedish reports state that mercury compounds
in sediments are methylated and thereby released into the water but data are
limited. An investigation has been designed to determine the rale of mobilization
of mercury compounds including mercuric sulphide by oxygenated and oxygen-
deficient bottom sediments. The extent of methylation and the uptake of solubilized
mercury by living fish will be determined. The rate and degree of mobilization of
mercury in sediments must be established in order to estimate the time required
for the dissipation of mercury from a river or lake.
Other studies include the use of caged fish as indicators of mercury pollution in rivers, and mercury levels throughout the aquatic food chain With
particular reference to fish food organisms. American Fisherics Socicty. 1960. Spccial Publication No.2.
Second Ed. Ann Arbor Michigan. 102p.
Bouveng, H.O. and P. Ullman. 1969. Reduction of Mercury Waste Waters from
Chlorine Plants. Swedish Water and Air Pollution Research Laboratory.
Stockholm, Swedcn. April 1969.
Fimreite, N. 1969. Mercury Uses in Canada and their possible Hazards as
Sources of Mercury Contamination. Canadian Wildlife Service,
Section, Manuscript Rep!. No. 17: 19p.
George, J.G. 1968. Mercury. Canadian Minerals Yearbook.
Hannerz, L. 1968. Experimental Investigation on the Accumulation of Mercury
in Water Organisms. National Nature Conservancy Board Drottningholm.
Sweden. Report No. 48: 120-176.
Jensen. S. 1969. Felkallor och konfirmarion vid bestamning av
metyikvicksilverradikalen. Nordisk Hygienisk Tidskrift, 50(2):
(FRB Translation Series No. 1394, 1970- "Sources of Error and Confirmation
in the Determination of Methylmercury Radicals. tt)
Jensen, S. and A. Jernelov. 1969. Biological Methylation of Mercury in
Aquatic Organisms. Nature 223: 753-754.
Lofroth. G. 1969. Methylmercury. Swedish Natural Science Research Council,
Stockholm, Sweden. March 20, 1969.
Rucker.R.R. and D.F. Amend. 1969. Absorption and Retention of Organic
Mercurials by Rainbow Trout and Chinook and Sockeye Salmon. The
Progressive Fish-Culturist, 31: 197-201.
Uthe, J.F., F.A.J. Armstrong and M.P. Stainton. 1970. Mercury determination
in fish samples by wet digestion and flameless atomic absorption spectrophotometry (In prell ]. Fish Res. Bd. Canada).
Wobeller, G., N.D. Nielson, R.H. Dunlop and F.M. Alton. 1970. Mercury
Concentrations in Tissues of Fish from the Saskatchewan River (in press
]. Fish. Res. Bd. Canada). CANADIAN------CONSUMPTION OF MERCURY IN 1967
Chemical Industry
Electrical Industry
Gold Recovery
1. Chlor-alkall Industry. 2. Electrical - fluorescent lights; sWitches; batteries. 3. ~::tnr~~e:::~ew proofing. 4. 5. Agriculture-fungicides. 6. 7. ~::::::;:U-tl~I:lssti_CSs'kirtdiseases. 8. Dental preparations. 9. General laboratory use.
(see George, 1968) Tablell-Chlor-AlkallPlantslnCanada
"FMC Chemicals Ltd.
Cominco Ltd., (closed 1969)
Hooker Chemicals Ltd. Plants: Nanalmo, B.C. North Vancouver, B.C.
Canadian Chemical Co., division of Chemcell Ltd. ,(closed 1969)
·lnterprovincialCooperative Saskatoon, Sask.
Dryden Chemicals Ltd.,
-Dryden Chemicals Co. Dryden, Ont.
"Dow Chemical Ltd. Thunder Bay, Ont.
-American Can. Co.
Brown Forest Industries Ltd. Espanola, Ont.
Shawinigan, Que.
-Aluminum Co. of Canada
·Standard Chemical Co. Ltd. Beauharnois, Que.
·Shawinigan Chemicals Lrd.(closed about 1968) Shawinlgan, Que.
Lebel - sur - Quevillon, Que.
"Canso Chemicals (to open 1970) New Glasgow, N.S.
• use mercury cells. Table III . Metcury Levels In Fish from Saskatchewan River System-
No. of Standatd Samples ppm. Hg Deviation
Goldeye
Lake Winnipeg - Sheepshead
- Walleye
-Sauger
Cumberland House - Sturgeon
• Common names of fishes used in this manuscript are those prescribed by the American Fisheries Society. 1960. Table IV - Mercury Conrenr of Fish from Manitoba Lakes
No. of Ave. Samples ppm. Hg
Lake Winnipegosis Sauger
Walleye
Waileye
Sauger
Walleye
Dauphin Lake Walleye
Walleye
Sauger
Walleye Table V- Mercury Content of Lake Winnipeg Fi,h
Northern Walleye Sauger Sheep,head ~::~~w Pike
ppm Hg)
Sturgeon Bay
Poplar Point
Long Point
Grand Rapid,
PlaygreenLake Table VI - Mercury Content of River Fish
Species Ave.ppm Hg
Sauger
RedR.(Selklrk) N. Pike (large)
N. Pike (medium)
Sauger
Red R. (Lockport) Walleye
Sauger
RedR. (St. Norbert)
Winnipeg R. (Eleanor Lake) Walleye
Mooneye
SaskarchewanR. (Saskatoon) Saskatchewan R. (Clarkboro) Walleye
Goldeye 1.92;2.27;3.79 Table Vll - Mercury Content of Fish from Kenora Area
Ave. ppm Hg
Walleye
Burbot(gonad)
Burbot(1iver)
Sucker (gonad)
Walleye
Sauger
Lake of the Woods ------
Crappie
Walleye Table VIII - Mercury Content of Fish from the Great Lakes
No. of Ave. Samples ppm. Hg
Carp 1 0.22 Catfish 3 0.35 Sucker I 0.33 Yellow Perch 40 0.31 Walleye 2 0.41 I (1.43) Rainbow Trout 1 0.13 Sheepshead 1 0.38 Bass 2 0.53 Smell 8 0.15 Whitefish 1 0.11
Kokanee 0.07 Whitefish 0.14
Lake Huron Coho Salmon 0.20 (Northern) Whitefish (0.04
Lake Huron Coho Salmon 0.17 (Southern) 0.28 ~~:;:~ieSh 0.16
Lake Michigan
Bullhead 0.16 Cisco 0.10 Sucker 0.17 Yellow Perch 0.18 Walleye 0.25 Smelt 0.15
Bass 9 2.78 Bullhead 1 0.17 1 2.03 ~:;~iSh 2 1.42 Coho Salmon 1 0.11 Mooneye 1 2.90 ~~rStkheelrl:npgi~e 1 1.98 3 1.43 Salamander 1 6.31 Shad 1 0.79 Sheepshead 4 0.92 ~~:rkgeeron 2 2.24 15 1.81 Walleye 15 1.08 Table IX - Mercury Check Sample Results
B Laboratory ppm. Hg.
Food & Drug Directorate, Ottawa
University of Toronto
Provincial Laboratory. Manitoba
Provincial Laboratory, Saskatchewan
UnlversltyofSaskatchewan
Dept. of Agriculture, Saskatoon DETERMINATION OF MERCURY IN FISH SAMPLES (Taken from Urhe, Armstrong and Stainton, 1970)
Place 0.1 - 0.5 g sample in the bOllom of a 30 cc KJeldahl
flask, using the device shown in Figure 1 to ensure that no sample
is above the level of the acid during the soluhilization step.
Add4.0ccsulphuricacid(S.G.l.B4).
Incubate flasks in a shaking water bath at 50-60°C until a clear
solution is obtained. With fish samples the solution is a deep red-
brown, andan intense light50urce(e.g. a150wattspotlight
covered with aluminum foil wich a small hole in it) is useful for
checking the dissolution.
Remove samples from bath, allow to stand for 1 h, cool in ice.
Add 15 cc 6% w/v potassium permanganate solution. slowly, with
sWirling. Allow to stand 30 m, at room temperature.
Close flask with polyethylene stopper. Samples.t this stage may
be kept for at least a day before analysis Without apparent loss of mercury.
A source of trouble in the oxidation with permanganate is the use of
too vigorous conditions during the acid dissolution. Too mOuch heating can cause carbonization, after which samples cannot be completely oxidized by permanganate. The properly digested mixture contains much suspended material but this is mostly hydrated oxides of manganese, which should dissolve completely, to give a colourless clear or slightly opalescent solution in the last stage of the determination when the reductant Is added.
Perkin-Eimer Model 303 wltb automatic null recorder readout (303-0103)
Eltber of the Perkin Elmer Instruments may be used wltb a bollow- cathode mercury iamp 303-6044 ~~ a mercury lamp 303-0703 and discharge
lamp power supply.
10 mV cbart.recorder, cbart speed 8-12 Inches/h.
80rosilicate glass, with silica end windows 22 mm diameter, 1 mm thickness attached with epoxy cement. It Is also possible ro use'standard
silica 100 x 22 mm cylindrical absorptiometer cuvettes with two filling tubes.
Borosilicate glass with polytetrafluorethylene stopcocks as shown
in Figure 2.
Magnetic stirrer. air regulator, flowmeter (30-300 cc/min) stopwatcb,
compressed air supply, aspirator pump.
5g
109
20g
Prepare in order, cool, make to 1000 cc, mix, filter. ------Mercuric chloride Standard A Dissolve 0.134 g HgCl in water. make to 100 ccm in graduated flask. 2
1.00 cc = 1.00 mg Hg
Dilute 1.00 cc standard solution A above, to 100 ce. in graduated flask. using approximately 1N H2 S0 4
1.00cc=10.0pgHg
Stable1day
1. Set up A.A.S. with mercury lamp, and with flow-through cuvette
in place of burner.
Wavelength 253.7 I'm
Slit setting
Adjust wavelength for maximum energy; align cuvette for minimum absorbance.
2. Have apparatus empty and clean, with taps in positions shown in
Figure 2. Magnetic stirrer off. Air flow 250 cc/min.
3. The sample is received in 30 cc Kjeldahl flask. and contains sulphuric
acid, hydrated oxides of manganese and possibly some permanganate.
in a volume of about 20 ce. It is impottant to transfer all of the solid
material with the sample.
4. Place 50 ccreductant in a graduated cylinder.
Place sample in flask, and replace stopper A. Rinse Kjeldahl flask with
two 10 cc portions of the reductant and place rinsings and remainder of
reductant into funnel. Replace stopper B. Start magnetic stirrer.
5. Open taps 4 and 3 to add reductant to sample.
Start stopwatch. closetaps4and3. 6. After 60 ~ 2 seconds, open taps 2 and 3, and turn tap 1 120 0 clockwise
to divert air stream through funnel and flask.
7. Note maximum pen deflextlon on chart, return tap' to Initial
position••
8. Open stoppers A and B and tap 5 to empty the apparatus. Rinse funnel
9. Close tap 5, replace stoppers A and B, stop magnetic stirrer.
Apparatus Is ready for next sample.
------Blank determination
Since the blank has components from the reagents used In the digestion, and also from those In the reductant, It may be necessary to determine them separately If, for any reason the whole sample Is not used. Normally the total blank Is determined by carrying out the complete procedure of digestion and analysis With no sample.
A calibration curve should be prepared at least once dai ly or when operating conditions change This is best done with 20 cc portions of20 per cent v/v H2S04 in Kjeldahl flasks. to which known additions of mercury have been made.
A set of six, from 0.00 to 0.25/,g Hg is convenient. using mercuric chloride Figure 1. Device for placing sample at bortom of Kjeldahl flask.
Figure 2. Apparatus for volatilisation of mercury. Cuvelte is mounted in ~itg~~:.a7thn;~ atomic absorption instrument for absorbance measurement