1664 JoURNAL FTSHERIES RESEARCH BoARD oF cANADA, vot-. 26, No. 6, 1969

Also of note is the survival from up to six sojourns at sea. In all probabil itythe Big Salmon River stocks are not being harvested to the fullest extentby the angling fishery and by the commercial f i.sheries in the Bay of Fundyor further along the northeastern Atlantic coasts. The latter may be an in-dication that the migration of the Big Salmon River fish is very l imited andoccurs in areas of relatively l ight f ishing.

REFERENCES

Crr-oonwooo, W. L. 1927. The salmon of R. Grand Cascapedia, Canada. Proc. Roy. Soc.Edinburgh 47 142-147.

DvrroNo, J. R. 1963. Family Salmonidae, p. 457-502. .Ia Fishes of the western North At-lantic. Part 3. Memoirs Sears Foundation for Marine Research, Yale University, NewHaven, Connecticut.

Er,soN, P. F., ,q,No C. J. Knnsrvrlr,. 196+. Forest spraying and salmon angling. The AtlanticSalmon Journal, October 1964.

Moxzres, W. J. M. 1925. The salmon - its life history. William Blackwood and Sor.rs,

Edinburgh and London.1926. Salmon (Salmo salor) of the River Moisie, (eastern Canada). Proc. Roy. Soc.

Edinburgh, 45: 334-345.

Nelr-, G. H. 1933. Salmon of the River Ewe and Loch Maree. Fish., Scotland, Salmon

F i sh . , ( 1932 ) V : 14M.

TevBnNBn. 1958. Salmon fishing. The Londsdale Library, Vol. X. Seeley, Service and

Co.. L imi ted. London.

Wnrrn, H. C., .tNn J. C. Meocor. 1968. Atlantic salmon scales as records of spawning history.

J. Fish. Res. Bd. Canada 25: 2439-2441.

Dichrornate Reagent Decornposition and Carbon Estirnation

Rav G. WBsrBNnousB

Weyerhaeuser Company, Research D'ia'is'iottA,ir and, Water Management, Longa'iew, Wash'ington 98632, USA

WnsrBNnousc, Rav G. 1969. Dichromate reagent decomposition and carbon

est imat ion. J. F ish. Res. Bd. Canada 26: 1664-1667.Potassium dichromate in 33 N H2SOI decomposes to form reduced chromium salts.

When the dichromate reagent is stored in clear bottles at room temperature, it decomposes

at 3.7/6 per week; when in amber bot t les at room temperature, at 0.6210 per week.Dichromate decomposition results in trivalent chromiurn with the possible liberation of

oxygen, as reported by other workers.

Received December 16, 1968

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Porassrulr DTcHRoMATB in concentrated sulphuric acid has been uti l ized as

an oxidizing reagent for the estimation of carbon in water.

This laboratory has been using the semi-rnicro (Marshall and Orr, 1964)

colorimetric procedure. Particulate carbon is filtered onto glass fiber pads

and then oxidized with .05 N KzCrzO 7 in 33 N H2SO4. Phosphoric acid is used

for chloride removal prior to oxidation.During use of the laboratory-prepared dichromate reagent, we visually

observed the color change with storage time. New reagents produced the

same results. Absorbance measurements on reagent blanks Confirmed the

visual observations. A brief l i terature search disclosed the reagent was thought

to be stable (Strickland and Parsons, 1960; Johnson, l9+9).

A laboratory study was designed to measure the rate of dichromate

decomposition in 33 N sulphuric acid under several storage conditions' Chloride

contamination and laboratory cleanliness were init ially eliminated as possible

causes of decomPosition.

Method.- Potassium dichromate sulphuric acid reagent, 0.0509 N K2Cr2O7,^was prepared

from reaqent grade chemicals. The f inal HzSO+ concentrat ion was approxim.ately 33 N.ThE reaient solut ion tvas div ided inro three volumes and stored in c lean glass stoppered

bottles as follows:

Bottle Glass tYPe Storage TemP (C)

1 Clear, PYrex OPen shelf Room

2 Amber OPen shelf Room

3 Clear, PYrex Refrigerator 4

Each bottle containinq the standard reagent was tested weekly to determine if dichromate

was stable with time.

Results - Both l ight and temperature affected the storage stabil ity of

dichromate in strong H2SO4 (Fig. 1). Light was the dominant factor in tl-re

decomposition.Data on the dichromate stored in the clear bottle at room tempelatufe

was evaluated assuminq a first order rate law (Daniels and Alberty, 1955), i.e.

2 . 3 0 3 C oK : _ l l o g

C

where Co : concentration of KzCrzOt init ially present; and C : concentration

of K2Cr2O7 pfesent at any time l. Approximately 3.7/s of. the dichromate

per week was converted to reduced chromium salts. Analysis of the reagent

kept at roorn temperature in an amber bottle showed a decomposition rate

of 0.620/6 per \\ 'eek. A similar analysis i l ,-as not performed on the reagent

stored in the refrigerator, as these data are clearly not represented by a simple

decomposition model. The large change after 18 weeks (Fig. 1) may represent

external contamination rather than instabil ity.J. F

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1666 JoURNAL FISHERTES RESEARCH BoARD oF CANADA. voL.26. No. 6. 1969

Frc. 1. Decomposition of dichromate in 33N HzSOr. X, clear bottle, on shelf ; O, amberbottle, on shelf; O, clear bottle, in refrig-erator. Lines drawn from data analvsis bv

least squares (Hoel, 1958).

Discuss'ion - Epik and Orochko (1958) indicate that K2Cr2O7 is decom-posed by strong sulphuric acid according to the overall equation

2 Cr2O7 : +1 6H+ : 4 Cr*3 * 3Oz + 8H2O.

They studied decomposition in 16-33 w sulphuric acid. However, from thelimited data presented, their work indicates an increasing rate of dichromatedecomposition with respect to time and acid concentration. They do notshow data for dichromate in 33 N H2SO*.

Results of the laboratory rate data indicate the l imiting law for dichromatedecomposition in concentrated H2SO4 may be of the first order. The rate isprimarily dependent on the remaining dichromate and photo chemical ini-t iation.

The method, as outl ined by Marshall and Orr (1964), does not requirean oxidized reagent blank. They recommend a completely reduced reagentblank for instrumental use and assume dichromate H2SO4 reagent stability.Repeated use of their procedure, using nonrefrigerated reagent storage, willresult in erroneous estimates of carbon.

To minimize routine test problems when using the dichromate-sulphuricacid reagent, observe the following precautions: (1) store the prepared reagentunder refrigeration, preferably in an amber bottle; (2) discard the preparedreagent after 2 months; (3) always determine carbon values (or oxygen) bydifference from a reagent blank prepared for each series of samples.

Our experience with this reagent has shown that, with refrigeration,its stabil ity is maintained for 3-4 months. Changes which occur earlier than

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NorES 1667

months have been traced to laboratory cleanliness or chloride carryoverdisti l led water.

. Achnowled'gtnents - The laboratory assistance of Mr Allen Pinkham is gratefully ac-knowledged.

REFERENCES

DlNr!'ls, F., eNn R. A. Ar,spnrv. 1955. Physical chemistry. John Wiley and Sons, Inc.,New York. p. 318-332.

Errr<, P. A., eNn A. I. Onocnro. 1958. The dependence of the stability of some inorganiccompounds containing oxygen on the pH of the medium. J. Inorg. Chem. 3: 190.

Honr,, P. G. 1958. Introduction to mathematical statistics. 2nd ed. Tohn Wilev and Sons,Inc., New York. p. 126-129.

JouNsoN, M. J. 1949. A rapid micromethod for estimation of non-volatile organic matter.J . B io l . Chem. 181: 709.

Mensx.Lrr,, S. M., eNo A. P. Onn. 1964. Carbohydrate and organic matter in suspension inlock str iven during 1962. J. Marine Biol. Assoc. U.K. 44: 285.

SrntcrLlno, J. D. H., AND T. R. Pnnsoms. 1960. A manual of sea water analysis (withspecial reference to the more common micronutrients and to particulate organic material).Bul l . Fish. Res. Bd. Canada 125. 185 o.

A Method of Separating Invertebrates frorn Sedirnentsusing Longwave Ultraviolet Light and Fluorescent Dyes

ANnnBw- L. HaunroN

Fisheries Research Board, of CanadaFreshwater fnsLitttt.e, W'inn'ipe.g, Man.

HeurlroN, ANonnrv L. 1969. A method of separating invertebrates from sedi-ments using longwave ultraviolet light and fluorescent dyes. J. Fish. Res. Bd. Canada26t 1667-1672.

The suitability of nine different fluorescent dyes for selectively staining invertebratesin fresh and formalin-preserved sediments was evaluated. Rhodamine B was the mostsuitable and tap water was found to be a satisfactory solvent for the dye when fresh sampleswere being treated, whereas 70 and 957o ethanol were more suitable solvents when thedye was used on formalin-preserved samples. Most invertebrates stained a bright pink

and fluoresced a brilliant orange under longwave ultraviolet light. In contrast silt, sand,and most other unwanted components in the sample fluoresced very little if at all. Sortingtrials indicated that the use of this method often reduced the sorting time to about one-third of that required when the samples were sorted under visible light. This was partic-

ularly apparent when the organisms were small and the samples contained large amountsof sediment and debr is.

Received January 20, t969

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