ISO 19670:2017 pdf download – Fertilizers and soil conditioners — Solid urea aldehyde slow release fertilizer — General requirements. 3.2 cold water insoluble nitrogen CWIN insoluble nitrogen fractions in urea formaldehyde or methylene urea products that are insoluble in phosphate buffer solution (pH 7,5) or distilled water at 25 °C during a 15 min period 3.3 cold water soluble nitrogen CWSN soluble nitrogen fractions in urea formaldehyde or methylene urea products that are soluble in phosphate buffer solution (pH 7,5) or distilled water at 25 °C during a 15 min period Note 1 to entry: CWSN = Total nitrogen –...