Accoding to Poprishchin (the hero of Gogol's "Notes of a Madman" who imagines that he is the King of Spain Ferdinand VIII), "Letters are nonsense. Letters are written by apothecaries..."

P. P. ("Phree Pharmacy") are Percy de Prey's initials. One of Ada's lovers, Percy is associated with the hero of Gogol's Overcoat (1842), Akakiy Akakievich Bashmachkin (see my previous posts). AAB's surname comes from bashmak (shoe) and brings to mind old Paar of Chose and Zapater of Aardvark:

As Van Veen himself was to find out, at the time of his passionate research in terrology (then a branch of psychiatry) even the deepest thinkers, the purest philosophers, Paar of Chose and Zapater of Aardvark, were emotionally divided in their attitude toward the possibility that there existed' a distortive glass of our distorted glebe' as a scholar who desires to remain unnamed has put it with such euphonic wit. (Hm! Kveree-kveree, as poor Mlle L. used to say to Gavronsky. In Ada's hand.) (1.3)

Есть вещи, вещи,
которые... даже... (Акакий Акакиевич
любил, если помните, "плевелы речи",
и он как Наречье, мой гость восковой)

Before going to the Crimean War (where he perishes), Percy writes a letter to Van:

Dear Veen,

In a couple of days I must leave for a spell of military service abroad. If you desire to see me before I go I shall be glad to entertain you (and any other gentleman you might wish to bring along) at dawn tomorrow where the Maidenhair road crosses Tourbière Lane. If not, I beg you to confirm in a brief note that you bear me no grudge, just as no grudge is cherished in regard to you, sir, by your obedient servant

Percy de Prey (1.40)

Torfyanaya or La Tourbière is the handmaid Blanche's home village (1.36). It is from Blanche (who placed an anonymous note in Van's dinner jacket and whose name means "white;" cf. Belokonsk) that Van learns about another lover of Ada, the composer Philip Rack (1.41). His name seems to hint at the Spanish Inquisition. The Inquisition is mentioned by Gogol's Poprishchin:

Judging by all the circumstances, it seems to me as though I had fallen into the hands of the Inquisition, and as though the man whom I took to be the Chancellor was the Grand Inquisitor. But yet I cannot understand how the king could fall into the hands of the Inquisition. The affair may have been arranged by France — especially Polignac — he is a hound, that Polignac! He has sworn to compass my death, and now he is hunting me down. But I know, my friend, that you are only a tool of the English. They are clever fellows, and have a finger in every pie. All the world knows that France sneezes when England takes a pinch of snuff [nyukhaet tabak]. (the entry of "January in the same year, following after February")

Tabak (tobacco) sniffed by England brings to mind Ivan G. Tobak, Cordula de Prey's first husband. On the other hand, Ada smells of tobacco when she returns from her rambles in the woods where she met one of her lovers (presumably, Percy de Prey):

'Please note, everybody,' said Ada, 'how voulu that slip was!I like a smoke when I go mushrooming, but when I'm back, this horrid tease insists I smell of some romantic Turk or Albanian met in the woods.' (1.38)

Greg Erminin is also in love with Ada but is too shy to make a declaration. Greg's motorcycle Silentium (1.39) brings to mind the phrase repeated by Poprishchin (who is secretly in love with his chief's daughter) in his diary: Nichego, nichego, molchanie. (All righ, all right, but silence.)

But I feel much annoyed by an event which is about to take place tomorrow; at seven o’clock the earth is going to sit on the moon. This is foretold by the famous English chemist, Wellington. (the entry "Madrid. February 30")

lest' - flattery; adulation

kavardak - mess, muddle

postel' - bed

To be precise, in his memoir essay on the author of "Russia" Bunin compares Voloshin to an ancient Greek, priapus, sperm whale (kashalot), but not to Zeus (as I wrote in my previous post).