Acids & bases

Sodium hydroxide · NaOH

Density, dynamic viscosity and specific heat capacity of aqueous sodium hydroxide as a function of concentration and temperature, computed from the Laliberté (2009) aqueous-electrolyte correlation. Tabulated over 5–50 wt% and 20–100 °C.

Also known as: Caustic soda, Lye, Sodium hydrate
CAS number: 1310-73-2
Tabulated range: 5–50 wt% · 20–100 °C
Properties: Density · Dynamic viscosity · Specific heat capacity · Specific gravity

At 50 wt% · 20 °C

reference snapshot

Density: 1516.3kg/m³
Density: 1.5163g/cm³
Specific gravity: 1.519
Viscosity: 81.55cP
Specific heat: 3410J/kg·K

Explore

Read a value at any point

Move the sliders to interpolate between the tabulated grid points. The readout and chart never go outside the validated 5–50 wt% and 20–100 °C range, and every number is interpolated from the committed table below — nothing is computed from a chemistry model in your browser.

Interactive explorer

Values are interpolated between the tabulated grid points below — sliders stay within the validated 5–50 wt% and 20–100 °C range.

Concentration28 wt%

Temperature20 °C

Density: 1304.5 kg/m³
Density: 1.3045 g/cm³
Specific gravity: 1.307
Dynamic viscosity: 11.12 cP
Specific heat: 3535 J/kg·K

Density (kg/m³) vs wt% NaOH at 20 °C — Sodium hydroxide.

Why it matters

What the numbers tell you

At 50 wt% and 20 °C, aqueous sodium hydroxide has a density of about 1516 kg/m³ (1.516 g/cm³) — roughly 1.52× the density of water. Its dynamic viscosity is about 81.55 cP, against roughly 1 cP for water at the same temperature, and its specific heat is about 3.41 kJ/kg·K — about 82% of water's 4.18 kJ/kg·K. Those differences carry straight into volume-to-mass conversions, pump and pipe sizing, and the heat needed to change its temperature.

Common grades

A few working strengths

Properties at 20 °C for a handful of concentrations in everyday use, read from the committed grid (interpolated between tabulated points where a grade falls between them). The full table follows below.

wt% NaOH	°C	Density kg/m³	SG	Viscosity cP	Sp. heat J/kg·K
10	20	1108.5	1.110	1.778	3773
25	20	1272.8	1.275	7.886	3557
32	20	1346.2	1.349	16.71	3509
50	20	1516.3	1.519	81.55	3410

Sources

Where the numbers come from

Every value on this page is computed by a deterministic model — none is entered by hand. The generating method and the references it is checked against:

▸Laliberte, M. (2009). A Model for Calculating the Heat Capacity of Aqueous Solutions, with Updated Density and Viscosity Data. J. Chem. Eng. Data 54(6), 1725-1760. doi:10.1021/je8008123
▸Perry's Chemical Engineers' Handbook, 6th ed. (Perry & Green) - aqueous NaOH density table

Model: thermo==0.4.0 (chemicals==1.3.0) - Laliberte 2009 electrolyte correlation · Generated 2026-06-07

Validation

Checked against a cited value

The model is cross-checked at one independently cited reference point. The page is published only because this check passes.

Property / point	Density · 50 wt% · 20 °C
Cited reference value	1525.3 kg/m3
Model computed	1516.32 kg/m3
Error vs reference	0.589% (tolerance 1%)

Perry's Chemical Engineers' Handbook, 6th ed.. Perry, R.H. & Green, D.W. (eds.), Perry's Chemical Engineers' Handbook, 6th ed., aqueous sodium hydroxide density-concentration table: 50 wt% NaOH at 20 degC = 1.5253 g/cm3.

Full tables

Every tabulated point

Rows are temperature (°C); columns are concentration (wt% NaOH). Read the cell at the intersection. Specific gravity is density divided by the model water reference of 998.2 kg/m³ at 20 °C.

Density — kg/m³

°C \ wt%	5	10	15	20	25	30	35	40	45	50
20	1053.2	1108.5	1163.8	1218.7	1272.8	1325.7	1376.9	1426.0	1472.6	1516.3
25	1051.9	1107.1	1162.3	1217.1	1271.2	1324.2	1375.6	1425.0	1472.1	1516.3
30	1050.3	1105.3	1160.4	1215.2	1269.3	1322.4	1374.0	1423.8	1471.2	1516.0
35	1048.5	1103.3	1158.3	1213.1	1267.2	1320.4	1372.2	1422.3	1470.1	1515.4
40	1046.4	1101.1	1156.0	1210.7	1264.8	1318.1	1370.1	1420.5	1468.8	1514.7
45	1044.2	1098.7	1153.4	1208.1	1262.3	1315.6	1367.9	1418.5	1467.3	1513.7
50	1041.8	1096.1	1150.7	1205.3	1259.5	1312.9	1365.4	1416.4	1465.5	1512.6
55	1039.2	1093.4	1147.8	1202.3	1256.5	1310.1	1362.7	1414.0	1463.6	1511.2
60	1036.5	1090.4	1144.7	1199.1	1253.3	1307.0	1359.8	1411.4	1461.5	1509.7
65	1033.6	1087.3	1141.5	1195.8	1250.0	1303.7	1356.8	1408.7	1459.2	1508.0
70	1030.6	1084.1	1138.1	1192.3	1246.5	1300.3	1353.6	1405.8	1456.8	1506.2
75	1027.4	1080.7	1134.5	1188.6	1242.8	1296.8	1350.2	1402.8	1454.2	1504.2
80	1024.1	1077.2	1130.8	1184.9	1239.0	1293.0	1346.7	1399.6	1451.4	1502.0
85	1020.6	1073.5	1127.0	1180.9	1235.1	1289.2	1343.0	1396.2	1448.5	1499.7
90	1017.1	1069.7	1123.0	1176.8	1231.0	1285.2	1339.1	1392.7	1445.5	1497.2
95	1013.4	1065.8	1118.9	1172.6	1226.7	1281.0	1335.2	1389.0	1442.3	1494.6
100	1009.6	1061.7	1114.7	1168.3	1222.4	1276.7	1331.1	1385.2	1438.9	1491.9

Dynamic viscosity — cP (mPa·s)

°C \ wt%	5	10	15	20	25	30	35	40	45	50
20	1.208	1.778	2.821	4.671	7.886	13.27	21.86	34.91	54.06	81.55
25	1.068	1.547	2.404	3.888	6.398	10.48	16.77	25.99	39.03	57.02
30	0.952	1.360	2.076	3.289	5.291	8.459	13.20	19.93	29.11	41.35
35	0.856	1.207	1.813	2.821	4.448	6.960	10.62	15.66	22.32	30.93
40	0.775	1.081	1.600	2.448	3.792	5.822	8.705	12.57	17.54	23.75
45	0.706	0.974	1.424	2.148	3.274	4.940	7.254	10.28	14.06	18.66
50	0.646	0.884	1.278	1.902	2.857	4.245	6.132	8.542	11.48	14.96
55	0.595	0.807	1.154	1.698	2.517	3.688	5.249	7.199	9.521	12.21
60	0.550	0.741	1.050	1.527	2.237	3.236	4.543	6.144	8.008	10.11
65	0.510	0.683	0.960	1.382	2.003	2.864	3.972	5.302	6.819	8.492
70	0.475	0.633	0.882	1.258	1.806	2.554	3.503	4.622	5.871	7.219
75	0.444	0.588	0.814	1.152	1.638	2.294	3.114	4.064	5.105	6.204
80	0.417	0.549	0.754	1.060	1.494	2.074	2.788	3.602	4.478	5.384
85	0.392	0.514	0.702	0.979	1.370	1.885	2.512	3.216	3.960	4.714
90	0.369	0.482	0.655	0.908	1.262	1.723	2.277	2.891	3.527	4.161
95	0.349	0.454	0.614	0.846	1.167	1.582	2.076	2.613	3.163	3.699
100	0.331	0.429	0.577	0.790	1.083	1.459	1.901	2.376	2.853	3.310

Specific heat capacity — J/kg·K

°C \ wt%	5	10	15	20	25	30	35	40	45	50
20	3930	3773	3671	3604	3557	3521	3491	3463	3437	3410
25	3940	3789	3690	3622	3574	3536	3504	3474	3445	3417
30	3949	3803	3706	3639	3589	3549	3515	3484	3453	3423
35	3957	3816	3720	3653	3602	3561	3525	3492	3461	3429
40	3965	3827	3733	3665	3614	3571	3534	3500	3467	3435
45	3971	3837	3744	3676	3624	3580	3542	3507	3472	3439
50	3978	3846	3754	3686	3633	3588	3549	3512	3477	3443
55	3983	3854	3762	3694	3640	3595	3555	3518	3482	3447
60	3989	3861	3770	3702	3647	3601	3561	3522	3486	3450
65	3994	3867	3776	3708	3653	3607	3565	3527	3489	3453
70	3998	3872	3782	3713	3658	3611	3569	3530	3493	3456
75	4003	3877	3786	3718	3662	3615	3573	3533	3495	3459
80	4007	3881	3790	3721	3666	3618	3576	3536	3498	3461
85	4010	3884	3793	3724	3668	3621	3578	3538	3500	3463
90	4014	3886	3795	3725	3670	3622	3579	3539	3501	3464
95	4016	3887	3795	3725	3670	3622	3580	3540	3502	3465
100	4017	3887	3793	3724	3668	3621	3579	3540	3502	3465

Limitations

Before you use these numbers

▸Laliberte (2009) aqueous-electrolyte correlation for NaOH-water. Tabulated for 5-50 wt% over 20-100 degC; the lower temperature bound stays above the crystallisation region of strong caustic (50 wt% NaOH crystallises near 12 degC). Values are for preliminary design; verify against vendor data for critical service.
▸Values are tabulated only inside the 5–50 wt% and 20–100 °C ranges shown; the correlation is not extrapolated beyond them here.
▸Figures are for a pure sodium hydroxide–water system. Commercial grades contain impurities (for example chloride in some caustic grades) that shift density and viscosity; check the supplier's data sheet for a specific product.
▸Use for preliminary design; verify for critical service.

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