Cream of 'Tartar . 405

of vitriol, and spirit of nitre. But evenspirit of salt did not dissolve the wholeof it.

To observe the phenomena of this cal-cination more particularly, I made the pro-cess in an open crucible, which I kept in ared heat a long time. But when there wasno appearance of any farther change, andthe substance was pretty hard, I took itfrom the fire, on which it presently assumeda blackish, or dirty brown colour. Spiritof salt dissolved this substance with as muchrapidity, to all appearance, as it had donethe mere black coal of tartar in the formerexperiment, and expelled as much air fromit. It still, however, did not dissolve thewhole: for a dirty powder remained undis-solved.

Whether any chemist will think theseobservations of any value I cannot tell.Probably they are not of much consequence,but I thought it might be worth while justto mention them,