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The thermal properties of the complexes of cinchomeronic and dinicotinic acid with several divalent metal ions were determined by thermogravimetry (TG) and differential thermal analysis (DTA). For the thermal stability of the anhydrous compounds a sequence may be observed for the metal ions with cinchomeronic (3,4-H 2 PC) and dinicotinic acid (3,5-H 2 PC): The thermal stability of the pyridine carboxylic acid for each metal of the series is: dinicotinic > cinchomeronic The activation energy values for each thermal reaction were also calculated, using the Coats and Redfern algorism, by the Univac 1108 computer, by a program properly implemented for the statistical analysis of the data to obtain the reaction order and the activation parameters with the relative confidence limits.

The thermal properties of the complexes of ortho -, meta - and para -amino- benzenemonocarboxylic acids with nickel(II), copper(II), and zinc(II) are determined by TG and DTA. The activation energy values for the first decomposition step of the anhydrous compounds are also calculated. The thermal data are then examined and correlated with the structure of the compounds.

Studies of the complexes of pyridinecarboxylic acids with divalent metal ions as a function of the position of the carboxyl groups were extended. The thermal properties of the complexes of quinoline acid (pyridine-2,3-dicarboxylic acid) with several divalent metal ions were determined by thermogravimetry (TG) and differential thermal analysis (DTA). A correlation between these compounds and others obtained by reaction between the studied metal ions with similar acids (lutidinic acid (pyridine-2,4-dicarboxylic acid) and isocinchomeronic acid (pyridine-2,5-di-carboxylic acid) is discussed in terms of the position of the carboxyl group far from the aza group. The thermal stability of the metal complexes is in the order Mn(II) > Fe(II) > Zn(II) ⋍ Co(II) > Ni(II) > Cu(II).

Classroom instruction and self-instruction are compared in terms of instructional functions—stimulus presentation, student response, confirmation of response, and branching. Both the lecture method and self-instruction allow stimulus presentation in many variations by means of audiovisuals. Both allow student response, confirmation of response, and feedback to the teacher, though these are guaranteed to all students in self-instruction. Both allow branching—or slanting the presentation to the individual needs of the students, though self-instruction is particularly appropriate in this way. When working primarily within one format or the other, instruction can be improved by using a variety of audiovisual media to meet the requirements for stimulus presentation. The lecture format can be enhanced by borrowing from self-instructional methods the desirable techniques of student response, confirmation, and, to some extent, branching. But we must conclude that a variety of instructional methods is appropriate—because a variety of functions must be met. The logical plan is to combine methods and media to meet these needs most effectively and efficiently.

Recent investigations have indicated that resistance to extinction is an inverted U-shaped function of percentage of reinforcement. Grant and Schipper (1952) suggest that two processes are involved in producing this function: discrimination and learning. The greater the percentage of reinforcement during acquisition, the more discriminable is the acquisition phase from the extinction phase, thereby, producing fewer extinction responses. On the other hand with the CR near zero strength, the greater the percent reinforcement, the greater the effect on habit strength and the greater the number of extinction responses. Lewis (1960, p. 3 ) has pointed out that, "if Grant and Schipper are correct, the point of inflection of the inverted U-shaped function would need to vary with the degree of learning. The greater the degree of learning, the more the poinc of inflection should move toward the low end of rhe percentage scale. . . ." The present study1 was an attempt to test this hypothesis in a classical aversive-conditioning paradigm measuring resistance to extinction of the GSR. The general design was to test independent groups under one of six treatments utilizing three percentages of reinforcement ( lo%, 30%, 100% ) and two levels of acquisition ( 10, 30 trials). Procedz~re.-Thirty male undergraduate students at the University of Maryland were assigned to six groups with five in each group. Recording and shock electrodes were placed on the palmar surfaces of the hands and the fingers, respectively. S was told to get comfortable and that he would receive some electric shocks during the course of the experiment. He was further told he could terminate the experiment whenever he wished; but none chose to do so. Next, the shock level was obtained by determining when S could just noticeably detect any stimulation and then increasing the number of turns on the inductoriurn by one and one half. The shock was then presented and maintained at this level for the course of the study. The CS was a 5-sec. 1000-cps tone at 40 db that terminated with a .5-sec. electric shock. The 2 )( 3 design yielded six independent groups which received either 10 or 30 presentations of the CS paired with the UCS on lo%, 30%, or 100% of the trials. The extinction series began immediately after

We see short films as being of two types with two purposes: (1) educational films presenting limited topics; and (2) teaching films—discrete clips presenting stimuli and perhaps confirmation of response. It is this latter which we are calling ‘single-concept films,’ and which we feel contribute most effectively to the instructional process. Where do you get single-concept teaching films? First, since there are few available to meet your teaching needs, consider excerpting sequences from longer films; and second, assuming you still have unmet needs, consider the value of producing your own.