The widely used method of synthesizing HCl and DCl gases for infrared analysis by hydrolysis of benzoyl chloride includes a potentially dangerous final step whereby the frozen product is allowed to heat and expand into an infrared gas cell. The subsequent rapid rise in vapor pressure can "pop" open glass joints in the vacuum line and vent the sample in the face of the user. We describe an improvement on this procedure whereby the product is collected at atmospheric pressure in a large flask, which can subsequently be transferred to the vacuum line for expansion into the infrared gas cell under negative pressure. The alteration described herein is applicable to essentially any synthetic method of HCl and DCl gas or other hazardous gases of spectroscopic interest.

The method of continuous variation is applied to the reaction between barium chloride and diammonium hydrogen phosphate in neutral, acidic, and basic conditions. Depending on the medium, barium dihydrogen phosphate, barium hydrogen phosphate, or barium phosphate is precipitated. The precipitates are washed, dried, and weighed. Construction of a continuous variation plot for each condition leads to the deduction of the molecular formula of the phosphate precipitated. This experiment demonstrates the concept of stoichiometric relationships between ions in the formation of compounds and serves to give students practice in calculations involving limiting reagents.

A first-semester general chemistry laboratory experiment for college is described in which students carry out qualitative analysis to identify seven unknown colorless solutions. The experiment serves to correlate qualitative analysis with classification of reactions and can also be used in second-year or advanced-placement (AP) high school chemistry classes.