( 45 ) 



obeying to the law of Guldberg and Waage. By this equilibrium 

 reaction part of the precipitin molecules combines with the corre- 

 sponding quantity of molecules precipitinogen substance, while by the 

 side of this compound a certain quantity of each of the two components 

 remains in free state. The compound is partly precipitated and partly 

 remains dissolved. How much remains dissolved depends for the 

 greater part on the salt solution which is present, for the sediment 

 is soluble in Na Cl-solution. 



Besides this equilibrium reaction there is still another which 

 consists in this, that part of the precipitate combines with free 

 precipitinogen substance to a soluble compound. This reaction 

 too obeys the law of Guldberg and Waage. The case is to be 

 compared with the precipitation of Ca (OH)^ by COj. By excess of 

 CO, a part of the resulting Ca CO3 is transformed in a soluble 

 bicarbonate. So Ca H^ 0, takes the function of the precipitin and 

 CO3 that of the precipitinogen substance. 



Astronomy. — ''Observations of the total solar eclipse of August ZO, 

 1905 at Tortosa (Spain)." By J. Stein S.J. (Communicated 

 by Prof. H. G. van de Sande Bakhuyzen.) 



At the invitation of Mr. R. Cirera S. J., director of the new 

 "Observatorio del Ebro" I went to Tortosa towards the end of 

 June 1905 in order to take part in the observation of the total solar 

 eclipse. I was charged with making the measurements of the common 

 chords of the sun and moon at the beginning and at the end of the 

 eclipse and had also to determine the moments of the four contacts. 

 The results might perhaps contribute to the correction of the relative 

 places of the sun and moon. 



The determination of the co-ordinates was much facilitated by the 

 circumstance that the signals of the three points Espina, Gordo and 

 Montsia of the Spanish triangulation were visible at this place. The 

 measurements of the angles with a theodolite yielded the following 

 results: 



<p = 40°49' 13".43 ; X=lm 58s 18 east of Greenwich. 



In these results the spheroidal shape of the earth is accurately 

 taken into account. Later measurements made by Mr. J. Ubagh 

 gave the same results. Electric time-signals, directly telegraphed from 

 the Madrid observatory, gave for the longitude: 1"^ 58^8 east of 

 Greenwich, As the most probable value we have adopted 1™ 58^5, 



