Hf-scientific DRT-100B Research Turbidimeters Manual do Utilizador descarregar pdf (Página 14)

Page!6D R T-100B!!(5/00)

(B) STANDARD FORMAZIN SOLUTIONS

Calibration of this instrument is based on Formazin, a material which can be made by synthesis and

reproduced repeatedly within one percent. When properly mixed, it is uniform in the number, size and shape of its

particles, thus making it an ideal turbidity standard. The unit of measure, and thus the calibration of this instru-

ment is in Nephelometric Turbidity Units (NTU) based on Formazin.

Calibration samples may be obtained by diluting Formazin Stock Suspension using “turbidity-free”

water. Formazin Stock Suspension may be prepared by the user (Ref. A.W.W.A. “Standard Methods 17th

Edition”) or it may be purchased in kit form — H.F. Scientific Part No. 50040.

Each kit contains:

Contents Units Qty.

Instruction Manual ea. 1

Formazin 4000 NTU Stock Solution 500 ml 2

Turbidity-free 0.02 NTU water gal/4L 1

Selected Cuvettes ea. 4

Cuvette caps ea. 4

Reference Standard ea. 1

Pipettes graduated 1ml, 10ml, 25ml set 1

Shake Formazin Stock Suspension each time before pipetting to insure even dispersion of the suspen-

sion. Rinse cuvettes with solution they are to contain.

The following table gives the relationship between dilutions of the stock suspension and NTU’s. Be

sure to adequately mix the stock suspension prior to removing a portion for dilution.

NTU valueNTU value

NTU value

PipettePipette

Pipette

AmountAmount

Amount

Base FormazinBase Formazin

Base Formazin

olumetrolumetr

olumetr

ic Flaskic Flask

ic Flask

8.0 NTU 10.0ml 2.0ml of 4000 NTU 1000ml

800.0 NTU 10.0ml 20.0ml of 4000 NTU 100ml

NOTE: 1. When the prepared samples start to flocculate, they are unreliable and fresh ones must be made. This

will occur more rapidly for the lower value diluted suspensions.

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Hf-scientific DRT-100B Research Turbidimeters Manual do Utilizador Página 14