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Peelu means paramanu or atoms, and paka means the transformation or change brought about in their relationship under the influence of heat and light. It is in this context that the reference made above and elsewhere to the fact that (i) the paramanus ( atoms and molecules ) do not occur in nature in an uncombined state, and (ii) they combine in twos, three, four, and so. on, to form molecules of Dwayanukas, Thrayanukas, Chaturanukas etc., becomes significant. The Vaiseshikas note that paramanus always combine, separate and recombine under the influence of heat and light or Tejas, which is of two kinds viz., endothermic and exothermic. The observed difference between one substance and another, or in fact, between all substances in regard to their colour, consistency, roughness, smoothness, etc., is held to be due to what is know as Pakabheda or difference in chemical reactions. " It is heat and heat alone that can cause transformation in respect of colour, taste, smell or physical characteristics of paramanus. These depend on (a) the nature of the constituent substances in contact; (b) the intensity or degree of heat described in terms of Khara, Mrudu and Madhyapakas and, (c) the species of the Tejas corpuscles that impinge on paramanus or atoms ( and molecules ) and the nature of the impact."

 

Stated in brief, the Vaiseshika school hold that " there is decomposition into homogeneous atoms (paramanus) transformation of atomic qualities ( qualities of paramanus) and finally their recombination, all under influence of heat and light."

 

The views expressed above are illustrated with the following example:

 

In the process of the baking of a raw clay pot by a otter, quick succession of changes are observed to take place in the material of the pot, in respect of its colour, density, consistency etc., similar to changes that take place during the process of the cooking of food. The Vaiseshikas interpret and explain the successive phases of transformation and change, as due to the decomposition of the pot in to their component atoms (paramanus) and their subsequent recombination under altered spatial relationship, different from their original disposition in the material of the raw clay pot before the same was subjected to the action of heat. The entire process of change in the molecular and atomic steps viz.,

                    i.            the decomposition of the material of the pot into its molecules, in the first stage;

                   ii.            the decomposition of the molecules into their constituent paramanus, in the second stage;

                 iii.            the recombination of the paramanus in new relationship and altered spatial alignments into molecules of two

 

paramanus - Dwaya - nukas: into molecules of three

paramanus - Thrayanukas, and into molecules of four

paramanus - Chaturnukas, and forth.

 

Thus, in the finished baked pot, the spatial relationship the originally existed between one paramanu and another in the material of the original unbaked clay pot is altered, and altogether new relationships are established resulting in the exhibition of new properties in respect of colour, density, consistency etc, of the baked pot.

 

The process of transformation and changes referred to above, in terms of Kala or

 

Time, are stated to take place as follows:

 

It takes nine moments or Kshanas for completion of the consummation of the change from the unbaked to baked state in the clay pot. In the first moment (Kshana), the Dvayanuka is destroyed. In the second moment (Kshana) the original black colour of the unbaked clay is destroyed. In the third moment (Kshana) a different colour - red - is generated due to the influence of heat and light. IN the fourth moment (Kshana) the paramanus combine to form the new substance. In the fifth moment (Kshana), the paramanus separate themselves from their old status (i.e) from their former place or the previous position. In the sixth moment (Kshana) they separate themselves again. In the seventh movement (Kshana) they combine with other paramanus. In the eighth moment (Kshana) they again align themselves as molecules of two paramanus (i.e) Dwayanukas. In the ninth moment (Kshana), the specific or the characteristic properties of the paramanus, such as colour, etc, manifest in the constituents of the material of the now fully baked pot. Thus, in nine moments (Kshanas), the soft, dark, unbaked clay pot is transformed into the hard and red baked pot.

 

It will be seen from the forgoing that the Vaiseshikas held that a raw clay jar or pot is baked, the old jar or pot as the case may be is destroyed, involving pari pasu the decomposition of the several compounds of its Dwayanukas. The production of new red colour in the molecules themselves is stated to be brought about by thermal influence on the compounds formed by them eventually producing a new jar or pot, as the case may be. The rapidity with which the successive steps in the process of transformation has been envisaged to occur is stated to prevent the eye from detecting each consecutive individual step. The following of purely the Nyaya school assert that, "the Tejas penetrates into the different compounds of two or more atoms (Paramanus) and thereby changes, not the jar, but its colour etc. The jar is still the same jar; only it is red and not black,"

 

The conception of physical and chemical changes of Vaiseshikas viz., the old theory of Peelupaka are suggestive of the following important facts of physical chemistry:

 (1) The paramanus, which as noted earlier correspond to matter described upto a few micrograms, and which for purposes of following and interpreting chemical reactions was found to be sufficient enough as now evidenced, are in a constant state of vibratory motion.

 (2) The Vaiseshikas have resolved all physical action into motion - molar, molecular and subtle - of mass, molecules and atoms respectively. This motion is stated to be of the whirling or rotatory and circular, and also harmonic (e.g. vibration) in kind. This motion, as noted earlier, is spoken of as 'parispanda.' All matter - atoms, molecules and aggregates of molecules - are always in a state of parispanda.

 (3) The fact that paramanus do not in nature occur in an uncombined state having been posited, the problem of what is known to-day as pseudo - unimolecular reaction does not arise and such a reaction is usually a rare phenomenon. The more common and frequent reaction as contemplated by the theory of two, three and four molecules, should remind us of bimolecular termolecular and still higher reactions of modern physical chemistry.

 (4) Physico - chemical changes and transformations involve contact between and collision of atoms and molecules respectively, a fact which is implied in Peelupaka.

 (5) Apart from the fact that associations and dissociations of paramanus or molecules in the consecutive steps of Peelupaka imply the utilisation and release of energy respectively, the fact that thermal influences take a leading part in accelerating or retarding the process of paka or reactions will also emerge. The theory of Peelupaka implies the formation of Exothermic compounds and Endothermic compounds.

 (6) Stated in terms of Kala or Time, the successive steps of changes and transformations envisaged in Peelupaka instanced with the example of the baking of the clay pot, is stated to occupy one Kshana or 2/45 of a second for each step.