Rod really doesn't know what he is talking about when
he refers to Morton, because Morton has not used YPS
since the late 1940's. I asked Morton, so I know.
Tom L.L.

By golly you're right Tom, my Morton's iodized table salt doesn't show it
on the ingredients list. But you're kind of missing the point, in that we
were talking about the anti-caking chemical and its possible toxic
relationship. In the future I will delete his 1 sentence reference to
Morton's. ) ~ jan

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On Mon, 02 Aug 2004 10:42:58 GMT, "ciel" wrote:

YPS (yellow prussiate of soda, sodium ferrocyanide) is a common
anti-caking additive in granulated table salt. It is potentially toxic to fish.

Table salt may contain up to 13 ppm YPS, and does not have to be
listed on the label, per FDA regulation (21 CFR 172.490).

When exposed to sunlight, ultraviolet light rapidly photolyzes YPS to
free cyanide. US EPA lists cyanide as toxic to fish at 0.022 ppm
(acute toxicity) to 0.005 ppm (chronic toxicity, "96 hr LC50" means it
kills half the fish in 3 days). Fortunately, cyanide isn't persistent; it
evaporates readily and bacteria can destroy it.

At the oft-recommended 0.1% salinity, salt with 13 ppm YPS would
put 0.013 ppm YPS in the pond, which could photolyze to 0.0044 ppm
HCN, which is near the toxic level.

If higher salinities were needed for disease treatment, cyanide could
exceed toxic levels.

If, on the other hand, lower salinities were used (e.g. 100 ppm for
prevention of nitrite toxicity), the low cyanide level would not be of
concern.

I use solar salt crystals, coarse 1/4 to 1/2 inch in size. It doesn't seem
to contain YPS (humidity causes it to fuse into a lump, which I break up
with a hammer or boot). An 80 pound bag was $6 on sale at Lowe's.
- Rod

Personally, I get Morton's water softener salt in the blue bag without
conditioners, 99.9% pure I think it says on it, no anti-caking chemicals
and only ~$4/40 lbs. ~ jan


(Do you know where your water quality is?)

~Power to the Porg, Flow On!~