RESEARCH
of Leiden, voiced this sentiment at the Inorganic Division dinner. Much of the progress in organic chemistry, said Van Arkel, was based on the early assumption (which fortunately turned out to be correct) that the molecular species in t h e solid, liquid, a n d dissolved states are identical to those in the vapor in equilibrium with solid or liquid. This assumption is not valid in solid state inorganic chemistry. W h a t is usually called inorganic chemistry actually embraces four rather different fields: • The chemistry of solutions in more or less polar solvents (including the chemistry of die coordination complexes). • The chemistry of the nonmetallic elements which is, like organic chemistry, essentially a vapor state chemistry. • The chemistry of metals a n d intermetallic compounds. • The chemistry of ionic compounds in t h e solid state. Taking the latter as his field, Van Arkel points out that it is not valid to assume that the molecular species will be the same in the solid as in t h e vapor phase. In fact, there are ordinarily no molecules in the solid state so there is no reason why compounds must be stoichiometric. As an example of erroneous reasoning carried over from organic chemistry, he cited the hypothesis that since there is such a compound as F e H 0 4 there should also be such a compound as Fe 3 Cl 8 . There isn't. One guide which has been very useful in clarifying much of solid state chemistry is the assumption that bonding is purely ionic. On this basis the chemistry of the oxides and halides of the metals in the first four groups can be developed logically. With the transition elements, some correction has to be applied for covalency. When allowance is made for nonionic character of the bonds, the chemistry of these elements can also be understood. Van Arkel defines true inorganic compounds as those in which t h e bonding is predominantly ionic. Reaction rates are so rapid that yields a r e essentially quantitative if the reaction goes at all. There are no isomers to cope with since only t h e most thermodynamically stable of the possible forms
can be isolated. Rates of exchange, between halogens for example, are so fast that mixed compounds like TiCl 3 Br cannot b e prepared in a state containing only one molecular species. With industry becoming increasingly interested in inorganic chemistry in such important fields as semiconductors, phosphors, ferrites, a n d metallurgy, the training of inorganic chemists is receiving concentrated attention. T h e education of the inorganic chemist poses many problems because of the diversity of the four general fields embraced by this discipline a n d because of t h e growing overlap between solid state inorganic chemistry and theoretical physics.
Measuring Lead in Air
m
That cars throw burnin g
NATIONAL
lead w h e n
MEETING
gasoline with T E L
in it has long been known. But how much and of what size distribution has not been known. Barbara J. Tufts of University of Chicago has found out. She told the Division of Industrial and Engineering Chemistry that, on the streets of Chicago, there is a maximum of about 40 micrograms of lead per cubic meter of air during periods of heavy traffic; that most of these lead particles are between 0.1 and 3 microns—the size range that is retained in the lungs and is thus potentially most dangerous; and that particle size distribution depends on the type of driving—stop-and-go driving gives larger particles than does a steady, faster pace. Miss Tufts collected samples from the Chicago streets by drawing air through Millipore filters. She then treated the filters with hydrofluoric acid fumes to solubilize lead compounds, neutralized with ammonia fumes, and exposed to tetrahydroxyquinone. The sample was then dried, mounted in immersion oil, and p u t under a microscope. Particle size distribution was determined from t h e size a n d number of red spots formed by reaction of lead with t h e organic reagent. Miss Tufts points out that Chicago's maximum level of 40 micrograms of lead p e r cubic meter of air is well below accepted tolerance limits for humans. Primi.ry value of her work, she says, is that it provides a w a y to Industrial & Engineering Chemistry
keep tabs on lead content in air—both from automobile traffic and from industrial wastes. In fact, she concludes, checking on industrial wastes would be more precise; the scientist would know the compounds with which he was working, whereas, in exhaust fumes, he must assume an average composition.
Hormones, Cancer Tie In Knowledge of relationship of tumor growth, hormones gives the chemist a cancerfighting tool
m
Hormones head NATIONAL ^ Parade of facMEETING tors that influence t u m o r growth, and Medicinal the most common Chemistry cancers, such as breast, thyroid, and prostate, are related to hormonal dysfunction. Patients with breast or prostate cancer are benefited w h e n organs that supply stimulating hormones are removed. Giving the patients antagonistic hormones also helps, Jacob Furth said at t h e Division of Medicinal Chemistry's Cancer Symposium on Metabolism and Clinical Problems. H e is associated with Children's Cancer Research Foundation in Boston. Furth says that help often comes too in thyroid tumor cases w h e n patients are given the thyroid hormone, a deficient restraining hormone. But hormone derangement is not t h e only force that makes many tumors grow. Lesser ones are a t work. Number of calories a person takes is one. It is found that under feeding reduces likelihood of tumor development and growth. Lack of vitamins can cause cancer and influence t h e rate it grows. Tumor cells are greedy and steal nutrients from the body pool, cutting t h e supply for normal cells. "Herein lies a vulnerable spot of tumors/' Furth claims. "They also grab avidly t h e antihormones and antimetabolites, and in so doing limit their own growth." That's why antihormones and antimetabolites are good drugs in holding down tumor growth. Example: Folic acid antagonists have beneficial effects in leukemias and in some tumors. Antibodies are a powerful defense against experimental grafted tumors, it has been shown. W h e n chemical a n d SEPT.
2 3,
1957 C&EN
75
