What's the difference between pure blue ink and blue-black ink?

The difference between pure blue ink and blue-black ink;

1, with different colors;

2. The composition difference is obvious;

3, the picture is on paper, and the preservation durability is different.

Pure blue ink is a dye ink made of acid ink blue, which has a single composition, smooth writing, non-stick pen and pure blue color, and belongs to acid ink. Blue aqueous solution, stable to acid, will deteriorate in case of alkali. Belonging to organic dye ink. Although its color is bright, its handwriting is not as strong as blue-black ink, and it is easy to fade. The font color after writing is bright pure blue. Suitable for general writing, poor stability, not easy to store for a long time, not suitable for writing files.

Blue-black ink, also known as iron tannic acid ink, is mainly composed of tannic acid (C4H 10O9) and gallic acid (C7H6O5? H2O) and ferrous sulfate (FeSO4) combine with each other to form ferrous tannic acid and ferrous gallate, which are insoluble high-valent iron after oxidation, namely ferric tannic acid and ferric gallate. The former enhances water resistance, while the latter enhances blackening, thus making the ink water-resistant, blackening and lasting in color. Therefore, blue-black ink is the first choice for general document writing, because it has a lasting and indelible feature.