Copper Sulfate Resistor Applet ## Definition:

#### Diagram    ## Calculate Properties of Solution:              top

### Special Values

D (diameter)
l (length)
R (resistance)

#### Outputs:

C's (conc. solute)

C'w (conc. water)

C's (alternate)

V (volume)

ρ (resistivity)

A (area) ## Output Format:top

 Select Format: Scientific Engineering Fixed ## Notes:top

• The alternate value for C'S is obtained from a fit to measured data found here.  This is a fit to measured data that covers much higher resistivities.  The equation is log(C's)=(log(1553)-log(ρ))/0.7465, where C'S is in g/l and ρ is in Ω-cm.

• You should use de-ionized water and copper electrodes to reduce resistance change over time.

• Example:  Suppose you want to make a 1000 ohm resistor out of 1" inner-diameter Tygon tubing with copper electrodes inserted at each end with 1 foot between electrodes.  The calculator gives C's=19.653 g/l and C'w= 991.41 g/l.  So, to make one liter of solution, fill a jar with 991.41 g of water and 19.653 g of CuSO4*5H2O (or make a smaller batch keeping the same proportions).  Note:  you could just add the amount, C's, to one liter of water with negligible error (you have to do this for the alternate version of C's).  Also, if you want to make just enough then use the volume (in liters) from the calculator and multiply this by C's to get the amount of CuSO4*5H2O you need, then fill with water.

• CuSO4*5H2O is know by several names (copper sulfate, cupric sulfate, cupric sulfate pentahydrate,...) and appears as blue crystals.

• Calculator assumes solution temperature of 20°C (68°F).  Actual resistance is a function of water temperature.

• In the table below, the left three columns are data from the CRC Handbook of Chemistry and Physics.  H% is the percent of hydrate (CuSO4*5H2O) by weight in the solution.  D204 is the relative density of the solution at 20°C compared to water at 4°C.  γ is the specific conductance at 20°C.  The right three columns are derived from the others for this calculator.

•  H% [by wt.] D204 γ [mS/cm] Cs'  [g/l] CW'     [g/l] ρ [Ω-m] 1.56 1.0085 5.4 15.7 992.8 1.852 3.13 1.0190 9.3 31.9 987.1 1.075 4.69 1.0296 12.8 48.3 981.3 0.781 6.26 1.0403 16.0 65.1 975.2 0.625 7.82 1.0511 19.0 82.2 968.9 0.526 9.39 1.0620 21.9 99.7 962.3 0.457 10.95 1.0730 24.6 117.5 955.5 0.407 12.52 1.0842 27.2 135.7 948.5 0.368 14.08 1.0955 29.7 154.2 941.3 0.337 15.64 1.1070 32.2 173.1 933.9 0.311 17.21 1.1186 34.4 192.5 926.1 0.291 18.77 1.1304 36.6 212.2 918.2 0.273 20.34 1.1424 38.6 232.4 910.0 0.259 21.90 1.1545 40.5 252.8 901.7 0.247 23.47 1.1669 42.3 273.9 893.0 0.236 25.03 1.1796 44.0 295.3 884.3 0.227 26.59 1.1926 45.6 317.1 875.5 0.219 28.16 1.2059 47.0 339.6 866.3 0.213

• Note that CRC Handbook gives values for Cs and Cw, but these count the 5H2O as part of the solution, not the solute, which would result in a slight error if not accounted for (this is why my values have the prime symbol).

• Density of 20oC water is actually 0.99823 [g/ml] from this table.

• If you want to use anhydrous CuSO4 (gray powder) then multiply amount of solute by 0.639 (you need less) and use more water given by the difference.