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There are three titles in the Acornsoft 'Chemical' series, although as yet I've been able to get my hands on only two of them, Chemical Analysis and Chemical Structures. Maybe Chemical Simulations is subject to one of Acornsoft's celebrated delays.

The Analysis program has three sections. These are, in tape version, curiously (and unnecessarily) loaded from a menu. Menus are fine on disc but frustrating on tape, particularly when their effect is the same as typing CHAIN"program name".

The three sections are Elements, Inorganic and Organic. All are fairly unadventurous quiz-type programs in which the student guesses the identity of a substance from data provided by the program. In each you can make a guess or ask for more information from a menu of tests. You score points for correct guesses. The programs are in Mode 7, without graphics and run without fiddling about on a standard model B with disc interface.

All three can perform a useful backup function in the study of chemistry for public exams. They are, of course, no substitute for practical work, nor for a skilled teacher, but could well add variety to essentially boring revision. Elements is aimed at 'O' level, while the other two are aimed higher, even at their 'easy' level. I found the misspelling of the plural of 'gas' highly irritating. Talk about illiterate scientists!

Attempts to list the program to discover the answers result in blank data statements so no cheating is allowed.

The Structures package contains two programs. Bonding produces semi-animated diagrams of the electron transfers and sharings involved in simple ionic and molecular bonding. (This is commonly known as the 'dot/cross' type of diagram.) 'Shapes' purports to produce 3D diagrams of molecular shapes. More of that later.

In both, you are invited to choose by symbol for a periodic table the elements to be investigated, a useful exercise in itself. Certain combinations are impossible and are forbidden by a useful colour-coding.

Bonding is too large to run on disc with the default setting of PAGE, but if PAGE is lowered to &1100, it can be transferred to disc. I found it admirable, aimed principally at the 'O'-level student, but providing useful revision material at 'A' level. Its only drawback is in giving the impression that some compounds are very complex, when the only problem is that data for them is not included in the program.

Shapes is a different kettle of fish. First, it is too large to transfer to disc without shifting. Second, it has an extremely limited repertoire of covalent compounds and tells you that simple ionic examples such as sodium chloride are too complex for it to draw (hardly confidence-boosting!). It purports to draw three-dimensional structures of the covalently bonded atoms, and the rotate the structure to aid understanding.

This can be much more satisfactorily done by 'ball and stick' models. Only three views of the structure are presented, and these are difficult to distinguish, even for tetrahedral molecules. But the clincher is that for linear molecules three identical views are drawn, one after another, with no way of skipping them. I would not show this rubbish to any of my classes, whatever the level.

These programs are provided with adequate documentation, including both pupil and teacher user guides. My overall opinion was that they were high on price, and rather low on ideas.