Salinity Table etc.

[R1Bill]

There seems to be an aweful lot of confusion related to salinity and PPT salt. The average Part Per Thousand (PPT) salt is what we are after. In most oceans (Red Sea Excepted) it is approximately 35 PPT. Since Salinity is related to temperature and PPT, it is only useful if you know what temperature your hydrometer is calibrated at and if you know what temperature your measurement is being taken at. On top of all of that most hydrometers (especially the floating arm kind) that you get at the LFS are complete JUNK. All IHMO of course

Here is a link to a lab grade certified hydrometer:

http://www.vwrsp.com/catalog/product...ect_id=0009308

Part# 34627-231 Certified 1.000 to 1.070 hydrometer

w/Shipping $31.52


Here is the table:

PPT
xx 59.00F 60.00F 68.00F 69.80F 71.60F 73.40F 75.20F 77.00F 78.80F 80.60F 82.00F 84.20F 86.00F

20 1.0145 1.0144 1.0134 1.0132 1.0130 1.0127 1.0124 1.0121 1.0118 1.0115 1.0112 1.0109 1.0106
21 1.0153 1.0152 1.0142 1.0140 1.0137 1.0135 1.0132 1.0129 1.0126 1.0123 1.0120 1.0116 1.0113
22 1.0160 1.0159 1.0150 1.0147 1.0144 1.0142 1.0139 1.0137 1.0134 1.0130 1.0127 1.0124 1.0120
23 1.0168 1.0167 1.0157 1.0155 1.0152 1.0150 1.0147 1.0144 1.0141 1.0138 1.0135 1.0132 1.0128
24 1.0175 1.0174 1.0164 1.0162 1.0160 1.0156 1.0154 1.0151 1.0148 1.0145 1.0142 1.0139 1.0135
25 1.0183 1.0182 1.0172 1.0170 1.0167 1.0165 1.0162 1.0159 1.0156 1.0153 1.0150 1.0146 1.0143
26 1.0191 1.0189 1.0180 1.0176 1.0174 1.0172 1.0169 1.0166 1.0163 1.0160 1.0157 1.0154 1.0150
27 1.0198 1.0197 1.0187 1.0185 1.0182 1.0180 1.0176 1.0174 1.0171 1.0168 1.0165 1.0162 1.0158
28 1.0206 1.0204 1.0195 1.0192 1.0189 1.0186 1.0184 1.0182 1.0179 1.0175 1.0172 1.0168 1.0165
29 1.0214 1.0212 1.0202 1.0200 1.0197 1.0195 1.0192 1.0189 1.0186 1.0183 1.0180 1.0175 1.0172
30 1.0222 1.0220 1.0210 1.0208 1.0205 1.0202 1.0199 1.0196 1.0193 1.0190 1.0187 1.0184 1.0180
31 1.0229 1.0227 1.0217 1.0215 1.0212 1.0209 1.0207 1.0204 1.0201 1.0198 1.0195 1.0192 1.0188
32 1.0237 1.0235 1.0225 1.0222 1.0219 1.0217 1.0214 1.0211 1.0208 1.0205 1.0202 1.0198 1.0195
33 1.0245 1.0243 1.0232 1.0230 1.0227 1.0225 1.0221 1.0218 1.0215 1.0212 1.0209 1.0205 1.0202
34 1.0252 1.0251 1.0240 1.0238 1.0235 1.0232 1.0229 1.0226 1.0223 1.0220 1.0217 1.0214 1.0210
35 1.0260 1.0258 1.0248 1.0245 1.0242 1.0240 1.0237 1.0234 1.0231 1.0228 1.0225 1.0221 1.0218
36 1.0268 1.0266 1.0255 1.0253 1.0250 1.0247 1.0245 1.0242 1.0238 1.0235 1.0232 1.0228 1.0225
37 1.0275 1.0273 1.0263 1.0260 1.0258 1.0255 1.0252 1.0249 1.0245 1.0242 1.0239 1.0236 1.0232
38 1.0283 1.0281 1.0271 1.0268 1.0265 1.0262 1.0259 1.0256 1.0253 1.0250 1.0247 1.0244 1.0240
39 1.0291 1.0289 1.0278 1.0275 1.0273 1.0270 1.0267 1.0264 1.0261 1.0258 1.0255 1.0251 1.0248
40 1.0299 1.0297 1.0286 1.0284 1.0281 1.0278 1.0274 1.0271 1.0268 1.0265 1.0262 1.0258 1.0255

First, this is how it works. You can use a 60 F (59F) table if it is set up like this one.
1. Using the temperature of your tank, go to the column that has approximately that temperature.
2. Scroll down until you see the SG you have on your hydrometer.
3. Now move straight across to the left, until you are in the column that has your hydrometer calibration
temperature (probably 77F for fish store and 59F or 60F for lab grade).
4. Read the SG at the calibration temperature in that column.
5. Now take that reading and go over to the second column and look for that SG reading and note its Salinity. That is the
salinity of your tank.

Example:

Tank @ 81 F (or 80.6 F)_and meter reads 1.022. The 77 F column shows 1.0226 ( rounded off is 1.023). Now look at column 2 for 1.023 (1.0229)_and the Salinity will equal 31ppt.....to low. If you are looking for normal Salinity of 35 ppt, your meter at 81 F would read about 1.025. Normal salinity is 35 ppt @ 1.026 in 77 F water with the meter calibrated to 77 F, so 1.026 -.001= 1.025 for 35 ppt_@ 81 F tank temp using a 77 F meter calibration _

conversion program:

http://www.phys.ocean.dal.ca/~kelley...r/density.html

If anybody wants this in an excel spreadsheet please email me and I'll send it.



Bill

[Heavenly Damsel]

I have a cheap swing arm hydrometer from the LFS, the very same thing you say is junk. Says on the package it is calibrated for tanks with temp between 68 and 80 degrees. Well I decided to test it's accuracy myself.....against the real thing. I took it to the beach. Water temps are running 78-80 at the beach these days. Well the reading in the ocean was 35ppt or 1.026.....reads the same in my tank which is at 80 degrees. Guess I lucked out and got a good one!

[R1Bill]

Heavenly Damsel,

The concept of the swing arm hydrometer is great. The problem is with the execution. Between air bubbles on the moving parts, friction, dirt, residue from previous measurements, I have not seen one that that will give you the same measurement on a consistent basis. I have one that is supposodly the "best" swing arm and I can't get the same measurement twice. That is why I recommend you get a known quantity. A simple, floating hydrometer that is lab grade and calibrated. $30 for such an important measurement. Why risk it?

Good Luck,

Bill