Additional Questions for the Fourth Book
[Quaestiones .1.1. annexae]
Why salt placed in water liquefies, but it does not liquefy when placed on a burning tile or in oil (or boiling honey).
One asks why it is that salt placed in water liquefies, but it does not liquefy when placed on a burning tile, but hardens instead. Similarly, when placed in oil or boiling honey, it does not liquefy.
In order to see this better, one must know that the generation of salt occurs from heat just as if that were its craftsman and from salt water as its matter. For the heat of the sun acting on the water consumes the more liquid and more subtle parts of it, and, once these are consumed, a thickening and hardening results and a transmutation into the essence of salt from the remaining thick and earthy parts.
Therefore, we say that when salt is placed on a hot tile with the heat acting on it, the more liquid parts are consumed and imperceptibly escape, and there occurs a greater thickening and hardening in the remaining thick parts. We perceive this on a newly made tile that is placed in the sun or on the fire; if it is left there for a long time, the action of the heat changes it. Since it does not encounter liquid and subtle parts on which to act, it acts on the solid parts and consumes and annihilates them, and thus destruction occurs. Similarly, salt placed in honey or oil does not liquefy, and this is because a blockage occurs from the viscosity and unctuousness of the oil. As a result, the liquid and subtle parts of the oil cannot penetrate [the salt] so as to effect a separation and liquefaction of the same [salt] by means of interspersing [the oil] between one part and another of the salt.
Similarly it does not liquefy in honey on account of its viscosity causing blockage in the pores, and this is why it is hardened in these two by their heat and dryness, whereas placed in water it liquefies. And this occurs because the fluid and more liquid parts of the water enter into the substance of the salt and separate part from part, and once separated these are softened; as a result of such separation and softening there occurs a liquefaction and a reduction to the proper matter.
Why musk placed among fragrant things loses its aroma and later, when placed in a foul-smelling place, it recovers its odor.
One asks why it is that when musk is placed among fragrant things it almost loses its aroma and later, when placed in a foul-smelling place (for example, when it is put into a latrine) it recovers its odor.
In order to see this better, one must know that an aromatic odor has to occur from a warm and dry complexion and from a subtle and pure substance, and it is necessary for every aromatic to be hot, both partially and totally, and to have a subtle substance. When, therefore, musk is placed among odoriferous things that are themselves warm and dry, and with the warmth and dryness of these others acting on it, that which is more subtle and pure in the musk is released, and thus the aroma that was contained in the musk but has been released is attracted by the odoriferous materials surrounding it, owing to the likeness that they bear toward the musk, and it is then consumed. That, however, which is thicker and more impure (the type of things that have no aroma in them) remains in the musk, and thus the odor of the musk is reduced.
Another reason that the odor of the musk is not perceived so well is because when a change occurs in the odors and properties of the other aromatic materials, then once the instrument [of smell] is placed nearby, the spirit of smell is changed by all of these others. Thus, when the soul is intent upon perceiving all the other properties, it cannot as fully perceive the odor of the musk. Thus, "intent on many, there is less for an individual of the senses."
But when it is put in a foul-smelling place, it recovers its own odor. Let us see why this is. A foul smell results from an accidental heat and a great deal of moisture and a crude substance. In the musk the fetid thing is preserved as a result of the moisture. The heat of the fetid thing acting on the musk resolves the heat of the musk, and, when it finds something contrary to itself, it struggles against it and gathers strength within itself, and, strengthened by this struggle and acting on the cruder parts of the musk, it resolves them into fiery parts, and purifies and refines them into aromatic parts. Another reason is that nature delights more in an odoriferous thing than a fetid one, and the musk, infected by the property and odor of the fetid thing, when it is placed near the nose, causes the soul, on account of its horror at the fetid odor, to perceive more fully and more avidly the odor of the musk, which is more delightful and friendly to it.
-  Cf. A., DA 22.214.171.124(75) (SZ2: 1552), where this muscus is defined as the exudation of a musk deer that is found on trees. It was probably some sort of resinous sap.