Polytechnic Association Proceedings. 699 



the adulterant in a given quantity of coffee mixture may be deter- 

 mined with sufficient accuracy for commercial purposes. 



ANALYSIS OF BLISTER STEEL. 



David Forbes, F. R. S., has communicated to The Chemical JVeios, 

 the results of his analysis of specimens of blister steel, which will 

 be examined with interest, because analyses of such steel are rare 

 and seldom found in chemical works. The per cent results are as 

 follows: Iron, 99.116; carbon, combined, 0.627; graphitic carbon, 

 0.102; manganese, 0.120; silicon, 0.030; sulphur, 0.005. No trace 

 of phosphorus was found, although search was made for it by sev- 

 eral different methods. 



whitwoeth's true planes. 



Mr. Whitworth, of England, proposes to place in the South Ken- 

 sington Museum, to be there perpetually preserved, three original 

 true planes and a measuring machine or instrument demonstrating 

 the millionth part of an inch, and further to make a sufficient endow- 

 ment to provide for the delivery of lectures to explain such instru- 

 ments. Their importance will be manifest when it is considered 

 that the value of everj'^ machine, when made of the best materials, 

 depends on the truth of its surfaces and the accurate measurement 

 of its parts. 



anti-incrustation solution. 



To prevent the formation of strongly adhesive sediments in a 

 steam-boiler, mix 125 kilograms of chrystalized chloride of barium 

 dissolved in 50 of water, with 25 kilograms of hydrochloric acid 

 having a specific gravity of 1.20; apply 15 parts by measure of 

 this acid solution to every 1,000 parts of water to be used in the 

 boiler. 



GAS from coffee. 



M. Babinet has reported to the French Academy the following 

 information with regard to the evolution of gas during the process 

 of making coffee. If finely-ground roasted coffee be steeped in 

 cold water, gas will be evolved to an extent about equal in volume 

 to the quantity of coffee used; and this action will take place very 

 rapidly, insomuch that if a bottle be half filled with coffee duly 

 ground, and the remaining space then filled with water until the 

 cork is reached, an explosion will ensue, sufficient in force to expel 

 the cork, or even break the bottle. 



