Reagents for Microchemical Analysis

A future column will detail a number of microchemical tests specifically suitable for conservation microscopy. In the meantime, Cargille™ has assembled two microchemical reagent sets (Set 1 and Set 2) that contain all the reagents you will need except for the acids, bases, solvents, and other liquids, which you will need to get from a chemical supply house. Set 2 coincides with Chamot and Mason, Handbook of Chemical Microscopy Volume 2, one of the most important single sources for microchemical test protocols; Set 1 coincides with Volume 1 in the set, and, while interesting, is less critical (Figure 4).

click image to enlarge (178K) The Cargille Chemical Microscopy Set 1 Figure 4

An easy test for Prussian blue is illustrated in Figures 5A and 5B, and Figures 6A and 6B show the results from two separate tests for lead white.

click image to enlarge (52K) Dispersion of Prussian blue in Meltmount™, refractive index 1.662, plane polarized light, 100X magnification Figure 5A

click image to enlarge (107K) Microchemical test for Prussian blue. A tiny drop of 10 % NaOH is added to the sample which slowly turns rust orange. The process can often be reversed by addition of acid Figure 5B

click image to enlarge (98K) Microchemical test for lead white. Addition of dilute HNO3 first produces bubbles of CO2; next, these crystals form. Plane polarized light, 100X magnification. Figure 6A

click image to enlarge (163K) Microchemical test for lead white. Addition of dilute HCl to the above reaction first produces the flat yellow crystals, then the blade-like forms. Plane polarized light, 100X magnification. Figure 6B