Dangerous Mixture: Trimethyl Phosphite and Magnesium Perchlomte
To the Editor: I n the interest of safety to your readers, the following report of a high-potential chemical accident is submitted for your information. Fortunately, the accident resulted in only minor injury to the employee, but it had every potential for very serious injury. The Accident
Using this procedure 130 students obtained preparations containing 65.6 =t4.0% Ni versus 64.8% theoretical for NiS. Professor Crouch found 64.4 + 1.8% Ni on four samples. The identification of the nickel sulfide powdered sample was achieved through the interpretation of its X-ray powder diffraction pattern. It was found that the observed relative intensities and d-spacings corresponded to those of nickel sulfide, NiS, as reported in the ASTM files, card catalog #2-1280. This corroborates previous analytical evidence supporting the claim that careful heating of Ni metal with S powder in a crucible will produce NiS alone. X-Ray powder photographs were taken a t room temperature (-25'C) with a Picker camera of 114.6-mm diameter and Ni-filtered Cu radiation (KG = 1.54178 A) produced on a Philips X-ray generator set for an exposure of 24 hr at 35 kV and 19 ma. The powder diffraction data, as corrected for expansion of the film during processing, are listed in the following table with the values reported for NiS on ASTM card #2-1280.
The employee was mixing solutes with organic solvents and measuring their physical properties in making a study of organic electrolyte systems for electrochemical power supplies. The work was being performed inside a ventilated hood, but the safety glass shield a t the front was left open approximately 10 in. to permit access of the employee's hands to his work. He was pouring trimethyl phosphite, (CH30)sP,from an open beaker into a 25-ml volumetric flask containing approximately 0.5 g of dry solid magnesium perchlorate, h'Ig(CIOn)p. Both the beaker and flask were being held in his hands. (He was wearing rubber gloves.) The instant the trimethyl phosphite came in contact with the magnesium perchlorate, therewasanimmediate flash followed by a loud report which was beard throughout the building. The employee received deep cuts on his hands and superficial cuts on his face. One lens of his safety glasses was shattered, which indicated that the glasses possibly prevented a serious eye injury. I n the investigation, it was learned that a thorough literature study had been made and the oxidizerorganic solvent reactions examined. In none of the literature was the hazard of explosion mentioned. This explosive reaction has been verified by repeated small-scale duplications of the above-described incident. This work was supported by the United States Atomic Within experimental error, the compound is NiS. Energy Commksion. No additional lines were observed to indicate impurities were present. The last seven lines could not be L. M. JERCINOVIC D. L. R o s ~ measured due to the fact that part of the diffraction pattern was not present on the film. SANDIA CORPORATION The weights and X-ray analysis are very convincing S A N D BASE,; ~A ALHUQUERQUII, NEWMKXICO 87115 evidence for NiS being the sulfide formed in this experiment.
Prepamtion of Nickel Sulfldes
To the Editor:
A note by Dingledy and Barnard [J. CHEM.EDUC., 44, 693 (1967)l reports the preparation of Ni3S2by the methods often used for preparing CuzS in the iutroductory chemistry laboratory. This is contrary to our experience with nickel by students and lab instructors a t both Swarthmore College and the University of Illinois. We find that with the following procedure NiS is obtained. Heat 1 g of powdered nickel mixed with 1 g of sulfur gently in a. covered crucible until flames of burning sulfur dissipate and then to red heat. Cool and weigh. Add 0.5 e of sulfur and repeat the heating, cooling, and weighing cycleuntil eonstant weight is achieved.
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Journal of Chemical Education
To the Editor: The method of Cullen, Crouch, and Haight is not exactly that used to prepare copper sulfide in the laboratory, and therefore d i e m from that described by Dr. Barnard and myself. It seems that the critical difference is the addition of more sulfur after the initial heating, leading by favorable transformation kinetics to the narrow aNil-, S solid solution phase region shown by Kullerud and Yund [J.Petrol, 3,126 (1962)],
which exsolves NiS (millerite) upon cooling to room the perspective which the student derives from an temperature. The spread of dat,a given for the stoihist,orical review of the origin and development of chiometry of millerite nickel sulfide aggrees with the principles. Not only does it provide for the student, width of this solid solution phase region at elevated an insight and often a better understanding of a printemperature. ciple than if it were presented as dogma but it emphaA paper scheduled for publication in THIS JOURNAL sizes the dynamic naturc of chemistry. F~rt~hermore, by Dingledy and Patrie will contain a statistical analif the scientists who were involved in the development ysis of results of student preparations of nickel sulof certain principles are cited, then the student becomes fide by the more usual method, resulting in heazlemore keenly aware of the fact that chcmistry today is woodite (Ni& average composition, but with an the cumulative product of the creativity of many perapparently larger standard deviation in student result,^. sons. More now than cver before is it important to emphasize that chemistry is not an abstract science totally detached from the real world and its problems hut is in reality a vital force in helping to solve them. An expression now in vogue may best describe what must be done if chemistry is to regain a good measure of its former allure: "Tell it, the way it is." THEODORE PE~~ROS THXGKOIKK W,\SHINGTON UNIVI,:RSITY WASHINGTON, D.C. 20006
Introductory Course for Both Science and Nonscience Majors
T o the Editor: The decreased interest in chemistry which has manifested itself recently is a development which should engage the interest of all chemistry instructors. I believe that this trend arises from the prevailing philosophy in chemical education. A system has been created whose product is the antithesis of its stated objective, viz., to stimulate interest in chemistry. I suggest that a reappraisal of the function and objectives of an introductory course in chemistry is in order. It is my conviction that an introductory course in any subject a t the freshman level should be open to every student admitted by an institution. The existence of separate courses for science and nonscience majors may have distinct pragmatic benefits but it destroys the very essence of a liberal arts education in which chemistry, as indeed any other science, is as equally accessible to a student as is any subject in the humanities. (It is understood that an honors program for advanced students should be available.) At the onset, the science and nonscience students are set apart when in reality an introductory course in chemistry can offer them rich rewards through its art, literature, history, and science to satisfy and stimulate their most diverse interests. This can be achieved with but a single course for science and nonscience majors without affecting adversely the level and catent for chemistry majors when related to the four year uudergraduate program. Admittedly time places a premium on any extensive discussion in lecture of the humanistic aspects of chemistry but experience has shown that they can be effectively introduced, if briefly, into any presentation of purely chemical topics without meaningful dilution of the latter. There is much to be said for
A Suggestion For Improving Student Seminars
To the Editor: Many student seminars are poorly given, and as a result, poorly attended. This occurs because even well prepared studcnts are accustomed to submitting only written mtterials. Oral presentation of materials still offersgrave problems to the inexperienced student. Since it is nec:ssary for graduate students to learn to present technical materials effectively,we have adopted a new techoiqu? for teaching students to do this. The student, in cooperation with the audio-visual department puts his seminar on video tape. Later, the student and the seminar inst,ructor view the tape, and the instructor and student together comment on the organiz&tion and presentation of thc material. Since the student is viewing himself, he can see the value of suggcst:ons and advice offeredby the instructor, and he can assess the possihle reception of his performance. The visual presenhtion is particularly useful in emphasizing to the student how effectively his blackboard material can be understood by his audience. We have found that the use of video tape helps the students prepare and give better seminars, since this technique encourages students to be object,ive about their performances. This technique could also be used to prepare inexperienced studcnts to give papers at. meetings.
Volume 45, Number 11, November 1968
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