HF scientific DRT-100B Research Turbidimeters - Manual (Page 14)

Page 6 DRT-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 value NTU value NTU value NTU value NTU value Pipette Pipette Pipette Pipette Pipette Amount Amount Amount Amount Amount Base Formazin Base Formazin Base Formazin Base Formazin Base Formazin V V V V Volumetr olumetr olumetr olumetr olumetric Flask ic Flask ic Flask ic 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.