October 2016

Salty pictures

Jean Hein

This summer I encountered two photos of salt that I would like to share with readers; both are of the salt from the Sifto mine in Goderich, Ontario. The mine extends under Lake Huron and is the world's largest underground salt mine.

The first (top right) was taken by Lew Brubacher, past Chem 13 News editor. Pictured is a bag of salt for his water softener. He was amused by the 100% natural label on the bag. We found more information on CrystalPlus on the Canadian Tire website “question and answer” page. Crystal Plus is typically 99.86% sodium chloride (salt), 0.05% moisture and 40 parts per million insolubles. The only additive is an iron build-up inhibitor called Resin Clean that is a food grade aliphatic acid.

I also took a photo of salt this week. Although it looks like a mountain of snow, it is a huge salt pile in Parry Sound, Ontario. My kids are standing in front of the pile (bottom right). You will notice a slight tint of blue. This salt is also from the Goderich Sifto mine. The salt is delivered by boat to Parry Sound harbour, which is the only practical deep water harbour on Eastern Georgian Bay for the road salt marine delivery. From this site, trucks start delivering the salt, and the pile is gone by the time spring arrives.

Salty student questions

1. Ask your students why the 100% natural label does not make sense.

2. What is the role of salt in a water softener? On roadways in the winter?

4. What is one difference between road salt and the water softener salt?

5. Based on the Canadian Tire website, answer the following questions about a bag of Crystal Plus. [Note the bag lists the mass as 20 kg but for these calculations, assume the mass has been measured to the nearest gram.]

a) How many grams of the Crystal Plus bag is NOT NaCl? Consider this the mass of the impurities. [28 g]

b) How many moles of sodium chloride are in one bag?
[340 moles]

c) How many grams of water are there in one bag? [10 g]

d) How many moles of water? [0.56 moles]

e) How many grams of insolubles in one bag? [0.8 g]

f) Why can’t the number of moles of insolubles be determined?

g) What could explain the number of grams of impurities not adding up to the mass of water and the insolubles?