F_{2} --> --C--C--C-- + HF
| | | | | |
F F F F F F

resulting in a teflon boned and shelled organism. He's going to be
tough to do much with. Diatoms leave strata of powdered teflon. The
main energy reaction is:

H H H
| | |
--C--C--C-- ... + F_{2} --> CF_{4} + HF
| | |
F F F

The blood catalyst metal is titanium, which results in colorless
arterial blood and violet veinous, as the titanium flips back and
forth between tri and tetra-valent states.

7. EFFECT ON INTRUDING ITEMS

Water decomposes into oxygen and hydrofluoric acid. All organic matter
(earth type) converts into oxygen, carbon tetrafluoride, hydrofluoric
acid, etc., with more or less speed. A rubber gas mask lasts about an
hour. Glass first frosts and then disappears. Plastics act like
rubber, only a little slower. The heavy metals, iron, nickel, copper,
monel, etc., stand up well, forming an insoluble coat of fluorides at
first and then doing nothing else.

8. WHY GO THERE?

Large natural crystals of fluorides, such as calcium difluoride,
titanium tetrafluoride, zirconium tetrafluoride, are extremely useful
in optical instruments of various forms. Uranium appears as uranium
hexafluoride, all ready for the diffusion process. Compounds of such
non-metals as boron are obtainable from the atmosphere in high purity
with very little trouble. All metallurgy must be electrical. There are
considerable deposits of beryllium, and they occur in high
concentration in its ores.

PROLOGUE

On Satan's Footstool

The big armor-tender vibrated, gently and not unpleasantly, as the
contragravity field alternated on and off, occasionally varying its
normal rate of five hundred to the second when some thermal updraft
lifted the vehicle and the automatic radar-altimeter control acted to
alter the frequency and lower it again. Sometimes it rocked slightly,
like a boat on the water, and, in the big screen which served in lieu
of a window at the front of the control cabin, the dingy-yellow
landscape would seem to tilt a little. If unshielded human eyes could
have endured the rays of Nu Puppis, Niflheim's primary, the whole scene
would have appeared a vivid Saint Patrick's Day green, the effect of
the blue-predominant light on the yellow atmosphere. The outside
'visor-pickup, however, was fitted with filters which blocked out the
gamma-rays and X-rays and most of the ultra-violet-rays, and added