ALD-52, also known as 1-acetyl-LSD, is a chemical analogue of lysergic acid diethylamide (LSD). It was originally discovered by Albert Hofmann but was not widely studied until the rise in popularity of psychedelics in the 1960s.
In Entry 26 of his compendium TiHKAL, which discussed LSD, Shulgin touched briefly on the subject of ALD-52. His writings are vague, second hand accounts, saying doses in the 50-175 µg range have resulted in various conclusions. He found that there was less visual distortion than with LSD and it seemed to produce less anxiety and tenseness and that it was somewhat less potent. Another informant claimed it was more effective in increasing blood pressure. Yet another informant could not tell them apart.
In The Hallucinogens by Hoffer and Osmond (1967), ALD-52 is listed as having a lower (approximately 1/5) intravenous toxicity (in rabbits), a lower (approximately 1/8) pyretogenic effect, an equal psychological effect in humans, and double the "antiserotonin" effect as compared with LSD.
Hey how about this
A little conversation tonight
Thinking aloud how we struggled to find
Our place in the dizzy heights
Don't often do this
We never really get the chance
Nearly froze to death on Oxford Street
Now we're sitting in the South of France
Talking through the evening
It's good to shoot the breeze
Just you and me on a balcony
And cicadas singing in the trees
Old '67 what a time it was
What a time of innocence, what a time we've lost
Raise a glass and have a laugh, have a laugh or two
Here's to old '67 and an older me and you
Sentimental twilight
Conversing on those virgin days
Laughing about how the two of us sound
Like a Tennessee Williams play
Honest, it's amazing
That we can get together at all
For in between the saddle and the grand piano
We can read the writing on the wall
Talking through the evening
Sitting here side by side
Just you and me on a balcony