Solution:
As2S3 is negative sol. For coagulating negative sol Al3+ is most effective. It is because higher the magnitude of the charge, the lower is coagulating value.
In coagulating the colloidal solution of As2S3 which has the minimum coagulating value ?
As2S3 is negative sol. For coagulating negative sol Al3+ is most effective. It is because higher the magnitude of the charge, the lower is coagulating value.