Exode 30:35

And confect therewith a fragrant incense, the work of the compounder, a pure and sacred mixture.

MEMULACH’ (SEASONED WITH SALT), PURE AND HOLY. This means that it be seasoned with salt of Sodom, just as the Rabbis have said: “Of salt of Sodom, the fourth part of a kab.” Onkelos translated [memulach as] m’areiv (mixed together). By this he intended to say that memulach means “rubbed out” — that the ingredients should all be so well-ground and mixed so thoroughly together, that their identity is “rubbed out” and none of the [individual] ingredients can be recognized. This is of the expression: For the heavens ‘nimlochu’ (shall vanish away) like smoke. Similarly: ‘u’vloyei m’lachim’ (and worn rags); A fruitful land ‘limleichah’ (into a salt waste). These are all expressions of destruction and annihilation.
And Rashi explained that the term memluach means that it be thoroughly mixed together in the grinding of the ingredients one with another. To this interpretation Rashi brought proof from the verse similar in meaning: ‘malachayich’ (thy mariners) and thy pilots, who are so called “because they turn over the water with the oars when they propel the ship, like a person who stirs up beaten eggs with a spoon in order to mix them thoroughly.”
In my opinion mariners are called malachim [of the root melach — salt] because they know the “taste” of the sea, as if they could feel if it is “salty” or “sweet;” that is to say, they know when it will be sweet and pleasant for those travelling by sea, and when it will be bad and bitter for them. It is not those who hold the oars [propelling the ship] who are called malachim [as Rashi said], for it is written on Tyre, The inhabitants of Sidon and Arvad were thy ‘shotim’ (rowers);, Verse 8. The elders of Gebal and the wise men thereof were in thee thy calkers; all the ships of the sea ‘u’malacheyhem’ (and their mariners) were in thee., Verse 9. For it is the older captains who know the sea that are called malachim. And it is further written, And all that handle the oar, ‘malachim’ (the mariners), and all the pilots of the sea, shall come down from their ships, they shall stand upon the land., Verse 29. Thus three categories are mentioned: those that handle the oar, the mariners, and the pilots [which proves that malachim — the mariners — are not those that handle the oar].
Similarly, a fruitful land ‘limleichah’ means “to a salt land,” for in a salt land nothing will grow, just as is written of Sodom, The whole land thereof is brimstone, and salt, and a burning, that it is not sown, nor beareth, and it is further written, and he sowed it with salt. It is possible that the letter lamed is redundant in the verse, for the heavens ‘nimlochu’ like smoke, the intent thereof being as in the word nimchu (erased), which would make it similar to these cases: ba’l'umim; (among the nations). wholly ‘shalanan’ (at ease) and quiet. (ease).

ממולח, thoroughly mixed. The word may reflect the word מלחים, sailors, oarsmen, as these mix and stir the waters which they row.

רקח, each of whom would collect different spices and after mixing them all they would become

מעשה רוקח, crushed, mixed, etc., a druggist’s handiwork. These various spices did not undergo uniform treatment at the hands of the spicer, druggist..

ממולח, thoroughly mixed, none of its ingredients remaining identifiable as separate substances.

טהור. refined to such a degree that it did not contain any foreign substances. The reason why this was of the essence was the fact that the burning up of the incense consisted of burning up the actual spices, derivatives or auxiliaries not being a part of that sacrifice at all. However, with the oil of anointing these extreme precautions did not apply seeing that it was in the nature of the ingredients that auxiliary components were not mixed with it or attached to it before the oil became refined.