Shweta Parpati is an Ayurvedic medicine in tablet or powder form.
uses: 
It is used in the treatment of dyspepsia, urinary calculi, difficulty in urination.
Effect on Tridosha: Balances Vata and Pitta.
Dosage:  125 – 500 mg,  once or twice a day before or after food or as directed by Ayurvedic doctor.
Sweta Parpati Ingredients:
Surya Kshara (Kalami sora / Soraka) – Purified Potassium nitrate – 16 grams
Sphatika  – Purified Potash Alum – 2 grams
Navasadara – Purified Ammonium chloride – 1 gram
All the ingredients are ground well, taken in mud vessel, heated, melted, poured on to an even surface, pressed to form thin white cakes (Parpati).
Unlike in other Parpati preparation, here, mud vessel is taken instead of iron vessel, and while heating, no ghee is added to the powder mixture.
Reference: Siddha Yoga Sangraha.