Mr Fuxit wrote:

"Sugar Soap" is a trade name for finely ground Sodium Carbonate (Washing
Soda).

Not quite:

Material Safety Data Sheet

SACHET & PACKAGING SERVICES LTD
SAFETY PRODUCT DATA SHEET
(in accordance with EEC Directive 91/155/EEC)

1.0 IDENTIFICATION OF PRODUCT/MANUFACTURE AND COMPANY

1.1 PRODUCT NAME / CODE : Sugar Soap Powder
[snip]

2.0 COMPOSITION/INFORMATION ON INGREDIENTS

2.1 Blend of Sodium Sesquicarbonate, Sodium Alkylbenzene Sulphonate (&)
Sodium Tripolyphosphate.

Some blends include sodium silicate as a mild abrasive.