Laboratory procedure notes

Caution This reaction involves highly toxic cyanide salts. It may be carried out safely, however, if prudent laboratory procedures are practiced. In particular, cyanide residues should be collected and disposed of separately (Note 1), and the entire sequence should be perform,ed in an efficient hood. 

Note The review of laboratory experiments in this book are not meant to replace detailed laboratory procedures, disposal and safety concerns. Under NO circumstances are the scenarios for the labs to be used as directions for actually performing the laboratory work. See the bibliography at the end of this book for a list of resources that provide detailed directions. 

Prepare all written materials that you will take into the laboratory. Be sure to include safety precautions and procedure notes. Use the data table below to record your data and observations. 

Note Essentially the same laboratory procedure was described by Rinkenbach in Kirk Othmer 8(1965), p 590. Prepn of SF was also described by Taylor Burton (See Addnl-Ref C for Sp). Prepn of sensitive form of SF was described by Taylor Rinkenbach (See AddnlRef D for SF)... 

A procedure for determining which factors are important is to use Sandel s Venn diagram approach. An adapted form is shown in Figure 10. Werni-mont has developed this idea for intra-laboratory studies. Note, however, that each of the three factors may be affected by external events. 

Workers in several laboratories have noted that the activity of urease appears to increase upon standing at room temperature. Until this is understood assay procedures cannot be assumed to yield precise values. 

Attempts to increase pyrite removal by increasing the reaction time met with limited success under our standard conditions because reaction of the ferric ion with the coal matrix depleted the ferric ion that was needed for extraction of the pyrite. Thus, for example, increasing the coal reaction time from 2 to 12 hrs only increased pyritic sulfur removal from 60 to 80% for Pittsburgh coal. Similar results were obtained for the other three coals. The only alternatives were to increase the amount of leach solution or to use a continuous or semi-continuous (multiple-batch) reactor. A multiple-batch mode was chosen because it was a simple laboratory procedure and at the same time it could approximate conditions encountered in a commercial plant. A 1-hr-per-batch leach time was used because our 2 hr results indicated that in the early stages of removal the rate begins to decrease after 1 hr, and six leaches (or batches) per run were used to assure that any pyrite that could be removed in a reasonable amount of time was removed. The progress of removal was monitored by analyzing the sulfate content in each spent leach solution elemental sulfur was not removed until all the leaches were completed. Table VII shows pyrite extraction as a function of successive leaches as followed by sulfate analysis of the leach solution. Note that the major portion of pyritic sulfur is removed in the first two leaches or 2 hrs, followed by lesser amounts in... 

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