In verifying the preparation procedure this author made the following variations.

• A safe light was used when working with occasionally observing with 100 watt incandescent lamps.  Light during venting outside at night or at other times was minimized.
• A tall Pyrex measuring cup (pint size) was used instead of the beaker.  It was advantageous to have a handle on the cup and the cost much less.
• A plastic (Lexan) knife (retired from a camping set) was used instead of a spatula and stir rod.
• About one half of the indicated proportion was made.  125 grams ferric nitrate was ordered and 143.85 grams received and used (mixed with 69.05 grams Oxalic Acid).
• In step 12, plastic wrap was placed on top of the absorbent towels which were placed on top of the material prior to striking and pressing with the gloved fist.  The entire stack would be placed on a flat plastic sheet rather then left in the container for this pressing effort.  As moisture would soak through the towels, this would keep things cleaner.
• Rather than leaving the container opened in the lab for the initial portion of Drying phase II, during the day, the container was kept closed in the lab; during the night, the container was placed outside and opened.  Provisions were made to block wind.  This was only done for one night.  While in the lab and for the remainder of drying, the open container was placed into a larger, covered container containing Calcium Oxide.
• It was suspected that the powder was not completely dry when used to mix a sample solution for testing.  Since the powder took 36 hours to dissolve as a 30% solution used for evaluation, there was not enough time to wait further.  The remainder of the powder will be left in the desiccator with calcium oxide until as dry as practical.

 
The following observations may appear as departures from the expected procedure and may be encountered by others.

• Considering the amount of fumes given off throughout the procedure, it is suggested that larger amounts (than called for in steps 1 and 2) be attempted using a scrubber hood (exhaust system which neutralizes the fumes).  A lot of nitric fumes are produced, but the amounts suggested should be manageable.
• Mixing took a good hour at 20^oC before a good liquid started. (Both the Ferric Nitrate and the Oxalic Acid were crystal.)
• Most of the mixing time was occupied with breaking up chunks.  This was rather easy by pressing the chunks between the knife and the side of the measuring cup.  Although there were many small chunks to break up.
• The solution remained grainy for several hours.  It seemed to take the route of a non-uniform mixture (described in step 5 of the procedure).  It eventually blended nicely as outlined in the procedure.
• Many absorbent paper towels will be used in this procedure during drying phase I and II.
• The  FO powder appeared to have a color much more green than the sample sent from Vicente and as depicted in the photos.  The Vizcay sample has a yellow color similar to that depicted  in the photographs. This green color is likely explained by the formation of large groupings as discussed in step 6.  The color is expected to shift toward yellow as the powder is pulverized and dried further.

 
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