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The soxhlet apparatus has been used in the laboratory to stimulate geochemical weathering; however, the high extraction temperatures required in the soxhlet do not represent a realistic simulation of the weathering environment. A modified design of the original soxhlet did not eliminate the problems of extraction temperature or inaccurate volumes of solvent passing through the sample. These problems were solved by moving the extraction chamber away from the upward path of the refluxing solvent. Extraction temperature differences (approximately 52°C) were responsible for higher concentrations of leachate metal in the original soxhlet leachate when a minesoil sample was weathered. This modification permits exact volumes of solvent to be passed through the sample, as well as a reduction in extraction temperature that would allow study of the role of bacteria in the weathering process.

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(University of Washington) drew our attention to a serious explosion in her laboratory during the purification of silver nitrate using the procedure in our book on the "Purification of Laboratory Chemicals", 2nd ed.; Pergamon: London, 1980, p 520. The following is quoted from her letter:As per your procedure the student was recrystallizing silver nitrate (20 g) from high purity (quartz-distilled, deionized) water (-100 mL) by the dropwise addition of high purity ethanol (-1 mL total). After collection of afirst cropof crystals (-7 g), the student, following normal crystallization procedures, produced a second crop of crystals by concentration of the mother liquor by heating on a steam bath, then dropwise addition of another -1 mL of ethanol. A contact explosion occurred during collection of the second crop when the student agitated the slurry on a sintered glass frit with a spatula. This explosion was quite violent, shattering the glassware involved and sending large chunks of glass as far as fifteen feet away. Very fortunately, the student was not cut by any of the glass shards; however, the potential for major personal injury was present.We were unaware of this danger, but explosions from silver nitrate and ethanol were known to occur and the haz- We are grateful to Professor Doherty for pointing out the dangers of this purification to us, and we should like to inform the chemical community of this grave error in our book. This will be rectified in the third edition. The disposal of toxic inorganic waste can create serious environmental problems and hazards. Contrarv to most organic waste, inorganic waste cannot be eliminated by incineration, and its proper disposal can be fairly expensive to most universities and industries. As long as the toxic substances remain in some soluble form they can eventually permeate into water supplies or otherwise pollute the surroundings.At this university I have found a practical way to trap hazardous inorganic lab waste and make its disposal safe. Aqueous solutions or suspensions of waste material are simply "frozen" in a rigid and insoluble matrix of Portland cement. This orocedure is best handled in a container lined with a bag. First, the arid waste is neutralized i n aslurr\~otslaked lime. Next, the rest ofthe waste isadded and etirrkd with sand and enough Portland cement to make 1016Journal of Chemical Education a mixture that can set up over night. The resulting block of concrete in the polyethylene bag can be buried safely a t a relatively minor cost. We would like to call attention to the danger of explosion of carbon disulfide in contact with ootassium metal. On following a recently published procedure (1) for the reduction of carbon disulfide with alkali metals, violent detonations have occurred in laboratories in France and the United States resulting, in one case, in hospitalization of the personnel involved. The threat of explosion of mixtures of carbon disulfide and potassium or potassium-sodium alloys has previously been noted (2).The Steimecke et al. proced...