Gardner colour scale

In Example 1 the results of producing hydroxylammonium acid sulphate by the conventional process and by the process according to th< invention were compared. In the preparation by the conventional process, a mixture of 4.8 moles of 1-nitropropane and sufficient water tc-make a total of 4 moles with that present in the sulphuric acid wa.-prepared and heated to reflux. There was then added 4.0 moles oi sulphuric acid, either electrolytic grade, 93% or C.P. grade, 96%. Tin. addition was made very slowly over a 3 to 4-hour period and tlu refluxing of the completed mixture was continued for a total reaction time of 8 hours. The reaction mixture was then cooled to below ahoui 115° C. and the two layers separated. The lower layer oi hydroxylammonium acid sulphate layer was analysed for HAf (hydroxylammonium acid sulphate) content and its colour determincM on the Gardner 1933 Standard Colour Scale. The upper layer Oi propionic acid layer was analysed for total acidity which. was corrected for sulphuric acid and hydroxylammonium acid sulphate content ami the per cent, yield of propionic acid calculated therefrom. The results oi these experiments are set out in Table 1A below. 

According to Cielab scale, colours were determined employing a colorimeter BYK Gardner. 

Colour Mixed colour for two-part adhesives, colour after cure. Those shown as, e.g. white- clear, have a colour change on curing. Thermoplastics - may state a colour numerically to the Gardner Scale. Silicones Various -several colour available, but product code may differ for coloured variants. 

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