1880.] 



MicKOsoopiCAL jour:nal. 



147 



introduced. In this way fresh- 

 water diatoms may be mixed with 

 those from marine sources, and 

 great confusion may result. In 

 every case, therefore, where water 

 is mentioned in these papers, fil- 

 tered water is meant. 



SULPHURIC ACID PROCESS. 



This process is applicable to al- 

 most every gathering, whether of 

 recent or fossil forms. When the 

 gathering consists of diatoms with- 

 out much mineral matter, and the 

 principal object of the cleaning is 

 to oxidize organic matter, it is not 

 necessary to go through the opera- 

 tions numbered 7 and 8, but pro- 

 ceed directly with operation 9. 

 However, in order to make this 

 process applicable to almost every 

 case, we give it in detail. We 

 would advise its use when fossil de- 

 posits are to be cleaned ; with fresh 

 gatherings which contain much ex- 

 traneous organic matter (a large 

 admixture of Confervae for exam- 

 ple), and with all specimens which 

 contain much mineral matter (lime, 

 magnesia, clay, silica, etc.). It will 

 be found a particularly good pro- 

 cess for guanos and mineral depos- 

 its generally. 



6. Disintegrate the material, if 

 necessary, by one of the following 

 processes : 



a. Place the lumps in a suitable 

 glass, porcelain, or iron vessel, pour 

 on a quantity of water suflficient to 

 cover them, and shave in some 

 common hard soap, so as to make a 

 rather strong solution of soap. 

 Set the dish on the stove where the 

 mass will boil slowly for several 

 hours, replacing the water as it 

 evaporates. The boiling will prob- 

 ably reduce most of the mass to the 

 condition of a tine powder. Pick 

 out the lumps which remain, or 

 pass the mass through a fine sieve, 

 and after washing the fine material, 



to remove the soap, proceed to the 

 next operation (7). This is proba- 

 bly the best process for siliceous 

 deposits. 



0. Boil the lumps in a solution of 

 washing-soda, in the same manner 

 as described in a. 



0. Boil in filtered water alone, for 

 several hours. This process serves 

 very well in some cases, as with loose 

 clays, marls, etc. 



d. Calcareous deposits, as chalks 

 and marls, may be most easily dis- 

 integrated by boiling in water acidi- 

 fied with hydrochloric acid. Just 

 suflicient acid should be added to 

 maintain a constant, but not very 

 rapid, evolution of gas. 



It lias been advised to boil the 

 highly siliceous deposits in strong 

 alkali, but except in the case 

 of specimens which resist tlie 

 long continued action of the soap 

 solution (a), such severe treatment 

 is not advisable. Alkaline solutions 

 act upon the silica of the frus- 

 tules and would eventually dissolve 

 them, but the soap solution does 

 not seem to act so rapidly as the 

 caustic alkalies or their carbonates. 



These processes for disintegrating 

 masses containing diatoms will be 

 successful for most specimens, but 

 they cannot be expected to succeed 

 in every case. When they seem to 

 fail completely, try boiling in strong 

 hydrochloric acid ; if this fails, try 

 strong sulphuric acid. 



7. The fine powder from opera- 

 tion 6, while still moist, or the fresh 

 material, either wet or dry, should 

 be treated with rather strong hy- 

 drochloric acid by boiling in a test- 

 tube, or a glass beaker for a few 

 minutes. This boiling removes 

 most of the mineral matters — lime, 

 magnesia, iron, and at least a part 

 of the alumina. The presence of 

 any appreciable quantity of iron 

 will cause the acid to assume a yel- 

 low color; if efferves(*ence takes 



