Refractometer

[backwoodssteve]

I have a very good refractometer but it is made to measure Brix. Is there any way to use it to measure salinity. Or should I just buy another one.

 

[rayn]

Little research, but didn't find a conversion scale. For the 40 bucks for a salinity one it may just be worth getting one.

 

[Randy Holmes-Farley Verified Community Expert]

Yes, you may be able to use it, but many are not adequately precise to really distinguish the salinities we are concerned with.

I discuss it here:

Refractometers and Salinity Measurement by Randy Holmes-Farley - Reefkeeping.com

from it:

Brix Refractometers
A commonly manufactured type of refractometer is called a Brix refractometer. Its scale usually reads in Brix, or % Brix (percent Brix). These refractometers are used in many industries to measure the concentration of sugar in water such as in the soft drink industry. They can be used to measure seawater's salinity, but are not always precise enough around the range of seawater's refractive index to be useful. A resolution of 0.2% Brix is common, and that is borderline acceptable for the reasons detailed below.


Table 4 shows the relationship between seawater salinity, refractive index and % Brix. If a refractometer has a resolution (not accuracy, but resolution, which is the finest amount it can distinguish) of 0.2 % Brix, then that translates to about +/- 1 ppt. So the best resolution would translate to 35 ppt seawater reading 34-36 ppt, which may be adequate for reef aquarists. A Brix refractometer that reads 0 to 10 % Brix with a resolution of 0.1% Brix might be a fine choice for determining seawater salinity in a reef aquarium, (although they are not inexpensive). Some Brix refractometers have a resolution of 0.5 % Brix or even 1% Brix, and they would not be suitable choices.

[TABLE="width: 60%, align: center"]
[TR]
[TD][TABLE="width: 455, align: center"]
[TR="bgcolor: #006699"]
[TD="colspan: 3"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]Table 4. The relationship between seawater salinity, refractive index and % Brix.[/SIZE][/FONT]​

[/TD]
[/TR]
[TR="bgcolor: #CCECFF"]
[TD="width: 181"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]Seawater Salinity (ppt)[/SIZE][/FONT]​

[/TD]
[TD="width: 184"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]Refractive Index[/SIZE][/FONT]​

[/TD]
[TD="width: 68"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]% Brix[/SIZE][/FONT]​

[/TD]
[/TR]
[TR="bgcolor: #CCECFF"]
[TD="width: 181"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]0[/SIZE][/FONT]​

[/TD]
[TD="width: 184"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]1.33300[/SIZE][/FONT]​

[/TD]
[TD="width: 68"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]0[/SIZE][/FONT]​

[/TD]
[/TR]
[TR="bgcolor: #CCECFF"]
[TD="width: 181"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]30[/SIZE][/FONT]​

[/TD]
[TD="width: 184"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]1.33851[/SIZE][/FONT]​

[/TD]
[TD="width: 68"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]3.8[/SIZE][/FONT]​

[/TD]
[/TR]
[TR="bgcolor: #CCECFF"]
[TD="width: 181, bgcolor: #CCECFF"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]31[/SIZE][/FONT]​

[/TD]
[TD="width: 184"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]1.33869[/SIZE][/FONT]​

[/TD]
[TD="width: 68"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]3.9[/SIZE][/FONT]​

[/TD]
[/TR]
[TR="bgcolor: #CCECFF"]
[TD="width: 181"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]32[/SIZE][/FONT]​

[/TD]
[TD="width: 184"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]1.33886[/SIZE][/FONT]​

[/TD]
[TD="width: 68"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]4.1[/SIZE][/FONT]​

[/TD]
[/TR]
[TR="bgcolor: #CCECFF"]
[TD="width: 181"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]33[/SIZE][/FONT]​

[/TD]
[TD="width: 184"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]1.33904[/SIZE][/FONT]​

[/TD]
[TD="width: 68"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]4.2[/SIZE][/FONT]​

[/TD]
[/TR]
[TR="bgcolor: #CCECFF"]
[TD="width: 181"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]34[/SIZE][/FONT]​

[/TD]
[TD="width: 184"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]1.33922[/SIZE][/FONT]​

[/TD]
[TD="width: 68"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]4.3[/SIZE][/FONT]​

[/TD]
[/TR]
[TR="bgcolor: #CCECFF"]
[TD="width: 181"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]35[/SIZE][/FONT]​

[/TD]
[TD="width: 184"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]1.33940[/SIZE][/FONT]​

[/TD]
[TD="width: 68"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]4.4[/SIZE][/FONT]​

[/TD]
[/TR]
[TR="bgcolor: #CCECFF"]
[TD="width: 181"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]36[/SIZE][/FONT]​

[/TD]
[TD="width: 184"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]1.33958[/SIZE][/FONT]​

[/TD]
[TD="width: 68"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]4.5[/SIZE][/FONT]​

[/TD]
[/TR]
[TR="bgcolor: #CCECFF"]
[TD="width: 181"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]37[/SIZE][/FONT]​

[/TD]
[TD="width: 184"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]1.33976[/SIZE][/FONT]​

[/TD]
[TD="width: 68"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]4.7[/SIZE][/FONT]​

[/TD]
[/TR]
[TR="bgcolor: #CCECFF"]
[TD="width: 181"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]38[/SIZE][/FONT]​

[/TD]
[TD="width: 184"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]1.33994[/SIZE][/FONT]​

[/TD]
[TD="width: 68"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]4.8[/SIZE][/FONT]​

[/TD]
[/TR]
[TR="bgcolor: #CCECFF"]
[TD="width: 181"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]39[/SIZE][/FONT]​

[/TD]
[TD="width: 184"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]1.34012[/SIZE][/FONT]​

[/TD]
[TD="width: 68"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]4.9[/SIZE][/FONT]​

[/TD]
[/TR]
[TR="bgcolor: #CCECFF"]
[TD="width: 181"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]40[/SIZE][/FONT]​

[/TD]
[TD="width: 184"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]1.34031[/SIZE][/FONT]​

[/TD]
[TD="width: 68"]

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]5.0[/SIZE][/FONT]​

[FONT=Georgia, Times New Roman, Times, serif][SIZE=-1]
[/SIZE][/FONT]
[/TD]
[/TR]
[/TABLE]
[/TD]
[/TR]
[/TABLE]

 

[backwoodssteve]

Thanks.

 

[Randy Holmes-Farley Verified Community Expert]

You're welcome.

Happy Reefing.