Measurement of turbidity – instrument ranges:\r To measure turbidity in the range up to about 1000 parts per million by the traditional candle standard, which instrument is used?

Introduction / Context:
Turbidity can be reported using different principles and scales. Historically, the Jackson candle turbidimeter measured turbidity in Jackson Turbidity Units, broadly corresponding to higher turbidity waters. Modern nephelometric turbidimeters measure low turbidity in NTU using scattered light at 90 degrees.

Given Data / Assumptions:

• Target range extends up to roughly 1000 ppm or high JTU values.
• Question references traditional instruments by name.

Concept / Approach:
The Jackson turbidimeter determines the depth at which a candle flame becomes obscured through the water column, suitable for relatively turbid samples. Nephelometers are preferred for low turbidity, typically 0 to 40 NTU or similar ranges, where sensitivity to small scatter is required.

Step-by-Step Reasoning:
Match the upper measurement range with instrument capability.Jackson turbidimeter covers higher turbidities up to about 1000 JTU.Therefore select Jackson turbidimeter for the stated range.

Verification / Alternative check:
Standard methods note the Jackson candle method is not suitable for very low turbidity where nephelometric techniques dominate, reinforcing the instrument selection for high ranges.

Why Other Options Are Wrong:

• Nephelometric turbidimeters excel at low turbidity ranges and precise NTU readings.
• Baylis and Hallige are not the standard names associated with the high range candle method.

Common Pitfalls:

• Assuming all turbidimeters measure the same range. Instrument selection must match expected turbidity.
• Confusing historic JTU scales with modern NTU units.

Final Answer:
Jackson turbidimeter