PR112 is known as Permanent Red in the Mission Gold (pictured) and Holbein lines, and Napthol Red for M. Graham. (Note that the color that Daniel Smith calls Permanent Red is a different pigment, PR170.)
Testing it in the Mission Gold line, I found PR112 Permanent Red to be a pleasant, middle red, similar in color to Pyrrol Red, but more transparent. It was easy to grade and mix.
Experiment Results
Hue: Somewhere between crimson and stop sign red. Grades through bright fire engine red to a “light red” pink that is neither orange-toned nor violet-toned.
Gradient: A pleasant, easy gradient without visible brush strokes. Not shiny in masstone!
Granulating: No, completely smooth.
Transparency: Semi-transparent.
Glazing: Crimson glaze.
Color Mixes: Not an all-star red mixer, I’d say; neither fantastic oranges nor purples. Coral with yellows. Grayish purples with blue.
What Others Say
On the lightfastness and versatility of PR112 (known as naphthol red):
This is one of several pigments where manufacturer and ASTM lightfastness tests disagree, possibly because the pigments tested were from different chemical suppliers. Many artists avoid all naphthol pigments as possibly too impermanent, and clearly the watercolor paint brand matters when the pigment is available from so many different pigment manufacturers worldwide. I suggest in these doubtful cases that you conduct your own lightfastness tests. My main objection is that these brilliant red paints are less flexible in mixtures than the perylenes or quinacridones, but when used unmixed, the rich hues are absolutely striking — many shades of lipstick attest to that!
Bruce McAvoy, handprint.com
My Overall Review
If I wanted a fire engine red, I think this would be a good option, although PR254 Pyrrol Red seems to be more popular in that slot. Personally, I find both colors too “on the nose” and I prefer to use a magenta or an orangey red, or a mix.