Reference Solution

A reference (standard) solution must always be calibrated for the pH meter before measuring pH. A buffer solution whose pH is unlikely to vary is used as the reference solution. Without a reliable reference solution, erroneous results can be expected.
Next, we will present five types of reference solutions specified in JIS, and the pH values of these solutions at each temperature.
Although it is not difficult to make these reference solutions, the process is troublesome if you do not have equipment for the purpose. It is more economical to purchase commercially available solutions.

Standard pH of Reference Solution, by Temperature
(JIS Z 8802 confirmed in 2011)

Temp(.C)
Temp(.C)	Nitrate Salt	Phthalate	Reference Solution Neutral Phosphate	Borate	Carbonate
0	1.67	4.01	6.98	9.46	10.32
5	1.67	4.01	6.95	9.39	(10.25)
10	1.67	4.00	6.92	9.33	10.18
15	1.67	4.00	6.90	9.27	(10.12)
20	1.68	4.00	6.88	9.22	(10.07)
25	1.68	4.01	6.86	9.18	10.02
30	1.69	4.01	6.85	9.14	(9.97)
35	1.69	4.02	6.84	9.10	(9.93)
38	---	---	---	---	9.91
40	1.70	4.03	6.84	9.07	---
45	1.70	4.04	6.83	9.04	---
50	1.71	4.06	6.83	9.01	---
55	1.72	4.08	6.84	8.99	---
60	1.73	4.10	6.84	8.96	---
70	1.74	4.12	6.85	8.93	---
80	1.77	4.16	6.86	8.89	---
90	1.80	4.20	6.88	8.85	---
95	1.81	4.23	6.89	8.83	---

Names and Composition of Reference Solutions

Name	Composition
Oxalate reference solution	0.05 mol/L potassium tetraoxalate KH₃ (C₂O₄) 2·2H₂O solution
Phthalate reference solution	0.05 mol/L potassium hydrogenphthalate C₆H₄(COOK)(COOH)solution
Neutral phosphate reference solution	0.025 mol/L monopotassium phosphate KH₂PO^4- 0.025 mol/L dibasic sodium phosphate Na₂HPO₄ solution
Borate reference solution	0.01 mol/L sodium borate (borax) Na₂B₄O₇·10H₂O solution
Carbonate reference solution	0.025 mol/L sodium bicarbonate NaHCO^3- 0.025 mol/L sodium carbonate Na₂CO₃ solution

Reference Solution

Index