In this chapter we examine the applications of proven experimental methods for the measurment of transport fluids to systems or conditions not extensively investigated at the time of the previous text. Interest in these new systems is driven more by industrial need than intrinsic scientific interest although the latter is not negligible. Molten metals and alloys feature in Sections 6.2 and 6.5 in the context of quite different methods, while molten silicon is treated in Section 6.4. On the other hand molten inorganic salts are discussed in Sections 6.3 and 6.4. Molten organic salts, also known as ionic liquids, are discussed in detail in Section 6.5.