When reading a meniscus, the analyst must be very careful that no error is introduced into the reading due to parallax. Under normal conditions, the chemist reads the meniscus on a horizontal “line-of-sight” at the bottom of the crescent-shaped body from the concave wetting of the liquid on the walls of the container (convex if it does not, i.e. mercury in a glass tube). Remember, the error associated with 0.1 in. water in reading the delta p was 2.4 % associated with the mass emission rate. One can read the incline manometers on the Method 5 sample box to within 0.05 in. water. Therefore, the error would only be very slight to the other possible errors in recording data and the operation of the sample train. This is also true for reading the delta h. When reading the delta h or delta p in the field, keep your “line-of-sight” horizontal and read the “bottom” of the crescent-shape of the meniscus.
Thank you for making it possible in a timely manner, it was much appreciated. We look forward to continued business with you in the future. Continue the great work at your establishment.
- Elisheba Bajnath (Analytical Testing Services), Marabella, Trinidad