Agricultural sulfur is used in the midwest by farmers who grow alfalfa. Back in the 1970's farmers in Iowa were seeing problems that more fertilizer did not solve. It was found that the soil was deficient in sulfur. Agricultural sulfur is sold in 50 lb bags, and the last time I checked, it was 89 cents per pound. But you need to go to a farmers co-op or similar to get a good price. Agricultural sulfur works great for lowering soil pH, I have been using it on our blueberry shrubs for several years. However, it takes about a year for the sulfur to be metabolized by bacteria in the soil, and converted to sulfuric acid. So the pH will not drop immediately, it will go down over time. With regard to fertilizing blueberries, I used Miracle-Gro for acid loving plants.

Muriate of Potash is synonymous with potassium chloride. The only other K fertilizers that are blended into "complete" fertilizers, I assume that is what you are looking for are as follows - Potassium slufate, potassium thiosulfate and potassium nitrate. In addition, if you dig deep enough, you might run into SulPoMag, Sulfate of Potash Magnesia which is used in the greenhouse industry.

The term K2O you see on fertilizer labels, I.E. %K2O is the way the percentage of potassium in the fertilizer product must be indicated, by law. Phosphorus will be labeled as %P2O5 and nitrogen as %N. If product is labeled as a "fertilizer" it must list the contents as described above, if it doesn't, it is a hoax product.

Sorry but, can't help you with finding a specific K fert. that fits the bill or help you with the chloride question. If you have lots of wood ash from the wood stove and acidic soils that need the pH raised, ash has potassium in it.

There is more to fertilizer labeling but my eyes are fried and it is late. check out this site to learn some very useful info. on fert. container labels

http://www.ncagr.gov/cyber/kidswrld/plant/label.htm